NEC electrical calculators
built for the field

Voltage Drop Calculator

Single- and three-phase AC drop. K-factor under #2 AWG, NEC Table 9 for #2 and larger. Flags the 3% and 5% NEC recommendations.

DC Voltage Drop Calculator

DC circuits (solar, battery banks, marine) using NEC Chapter 9, Table 8 resistance values.

Solar Voltage Drop Calculator

PV DC string and array conductors against the 2% and 3% solar design targets. Reports power loss; NEC Chapter 9, Table 8 resistance.

3-Phase Voltage Drop Calculator

Three-phase voltage drop using the √3 multiplier. NEC Table 9 AC resistance, same method as the main VD tool.

12V Voltage Drop Calculator

Automotive, RV, and battery systems. Defaults to 12V; override for 24V and 48V banks.

Extension Cord Voltage Drop

Match a cord gauge (16-10 AWG) to a tool load. Practical 3% guideline; K-factor method.

Marine Voltage Drop Calculator

Boat wiring per ABYC E-11: K = 10.75 copper formula, 3% critical and 10% non-critical limits, marine cable sizes 18 AWG to 4/0.

Voltage Drop Chart

Printable max-run-distance tables at the 3% recommendation, for 120V and 240V, copper and aluminum, by AWG and load.

Wire Size Calculator

Returns the minimum conductor for a load, distance, and target voltage drop. Checks NEC Table 310.16 ampacity, derating, and standard OCPD sizes.

Wire Gauge Calculator

Enter a required ampacity, get the minimum AWG. NEC Table 310.16 with full derating: ambient, conductor count, and 110.14(C) termination cap.

Wire Ampacity Calculator

Derated ampacity per NEC 310.15: ambient correction, conductor-count adjustment, and 110.14(C) termination cap.

Wire Ampacity Chart

Printable NEC Table 310.16 base ampacities for copper and aluminum, 60/75/90C columns, 18 AWG to 2000 kcmil. Computed from the audited ampacity calculator.

DC Wire Size Calculator

Sizes conductors for solar PV, battery banks, and 12/24/48V systems. Table 8 DC-resistance voltage drop plus Table 310.16 derated ampacity.

AWG Calculator

AWG/kcmil ↔ mm² conversions from the published NEC Chapter 9 Table 8 areas, with the IEC 60228 metric cross-reference.

Cable Size Calculator

Sizes each conductor of a multi-conductor cable when more than three current-carrying conductors are bundled, applying the NEC Table 310.15(C)(1) adjustment on top of Table 310.16 ampacity.

Dwelling Service Conductor Calculator

Minimum copper and aluminum service or feeder conductor for a 100 to 400 amp single-phase dwelling under the NEC 310.12 83% allowance, with the standard Table 310.16 size for comparison.

Ampacity Correction & Adjustment Calculator

Reads the NEC Table 310.15(B)(1) ambient temperature correction factor and Table 310.15(C)(1) conductor-count adjustment for a conductor, then reports the derated ampacity.

Parallel Conductor Sizing Calculator

Total ampacity of conductors run in parallel under NEC 310.10(G): the 1/0 minimum, per-conductor ampacity times the number of sets, the shared-raceway Table 310.15(C)(1) derating, and the 250.122(F) grounding conductor per raceway.

Conduit Fill Calculator

Mixed conductors in EMT, RMC, IMC, or PVC against the 53% / 31% / 40% limits in NEC Chapter 9, Table 1.

Conduit Size Calculator

Minimum conduit trade size for your conductor bundle across EMT, RMC, IMC, and PVC Schedule 40/80, all in one comparison table.

Cable Tray Fill Calculator

Multiconductor cable fill for ladder and ventilated trough trays per NEC Table 392.22(A), Columns 1 and 2, with the minimum standard tray width.

Wireway Fill Calculator

Conductor fill for metal and nonmetallic wireways against the NEC 376.22(A) / 378.22 20% limit, minimum standard size, and the over-30-conductor adjustment flag.

EMT Conduit Fill Calculator

Fill calculation locked to EMT. Minimum trade size and actual fill percentage for your conductor bundle.

PVC Conduit Fill Calculator

PVC Schedule 40 and Schedule 80 fill per NEC Chapter 9. Separate Table 4 areas applied for each schedule.

Conduit Fill Table

Max same-size conductor counts from NEC 2020 Annex C: EMT, IMC, RMC, PVC Sch 40/80. THHN/THWN-2 and XHHW-2. Printable.

PVC Conduit Expansion Calculator

Thermal length change of a straight PVC conduit run from the temperature swing per NEC Table 352.44, with the 1/4 inch expansion-fitting threshold and an optional direct-sunlight allowance.

Conduit Support Spacing Calculator

Maximum support spacing for PVC, RMC, EMT, FMC, and LFMC by trade size per NEC 352.30/344.30/358.30/348.30/350.30, with the box-securing distance and a support-point count for your run.

Cable Support Spacing Calculator

Maximum support interval for NM (Romex), AC, MC, and SE cable per NEC 334.30/320.30/330.30, with the box-securing distance and a support-point count for your run.

RTRC Conduit Expansion Calculator

Thermal length change of a straight RTRC (fiberglass) conduit run from the temperature swing per NEC Table 355.44, with the 1/4 inch expansion-fitting threshold and an optional direct-sunlight allowance.

Maximum Bends Between Pull Points Calculator

Add the bends in a conduit run and check the total against the NEC 360-degree limit (four quarter bends) between pull points per 358.26/344.26/352.26 and the other .26 sections, with offsets counted as two bends.

Cable Protection Setback Calculator

Check whether a cable or raceway in wood framing clears the NEC 300.4 1-1/4 inch setback or needs a 1/16 inch steel nail plate, for bored holes (300.4(A)(1)), notches (300.4(A)(2)), and parallel runs (300.4(D)).

Box Fill Calculator

Required outlet, switch, or junction box volume per NEC 314.16(B): conductor, clamp, support-fitting, device-yoke, and grounding allowances against the box capacity.

Pull Box Size Calculator

Minimum pull and junction box dimensions per NEC 314.28(A): straight pulls at 8x the largest raceway and angle or U pulls at 6x plus the row sum, for conductors 4 AWG and larger.

Fan & Luminaire Box Support Calculator

Can an outlet box support that paddle fan or luminaire per NEC 314.27? Checks the 35 lb unmarked fan-box limit, the 70 lb fan ceiling, and the 50 lb luminaire allowance, or flags independent support.

Breaker Size Calculator

Standard NEC 240.6(A) breaker for a load with the 125% continuous rule, plus the minimum conductor the breaker can legally protect.

Continuous Load Calculator

Apply the NEC 210.20(A) continuous-load rule both ways: size a breaker for a continuous load (125%), or find the maximum load an existing breaker can carry (the 80% rule).

Fuse Size Calculator

Standard NEC 240.6(A) fuse for a general-use load, including the fuse-only 1/3/6/10/601 A ratings, with the 125% continuous rule and the minimum conductor per 240.4(B)/(D).

Motor Breaker Sizing Calculator

Motor branch-circuit breaker or fuse per NEC Article 430: full-load current from Table 430.250, Table 430.52 device percentages, and the 430.22 conductor.

GFCI Breaker Sizing Calculator

Check whether NEC 2020 210.8 requires GFCI protection for a location, then size the GFCI breaker and conductor with the 1-pole or 2-pole call.

AFCI Requirement & Breaker Sizing Calculator

Check whether NEC 2020 210.12 requires arc-fault protection in a dwelling room, then size the AFCI breaker and conductor, with the 210.12(D) extension rule and the AFCI-vs-GFCI distinction.

Surge-Protective Device (SPD) Requirement Calculator

Check whether NEC 2020 230.67 requires a service surge-protective device, which Type (1 or 2) satisfies it, where it mounts, and how the 230.67(D) replacement trigger applies.

EV Charger Circuit Calculator

Branch-circuit breaker and wire for an EV charger: NEC Article 625 continuous-load rule sizes the circuit at 125% of the charger rating, with SAE J1772 Level 1/2 presets.

Transformer Sizing Calculator

Maximum primary and secondary overcurrent device for a transformer 1000V or less per NEC Table 450.3(B): rated current from kVA and the 125/167/250/300% limits.

MCA & MOCP Calculator

HVAC minimum circuit ampacity and maximum overcurrent protection per NEC Article 440: 125% conductor (440.33), 175%/225% device (440.22), and the Table 310.16 wire size.

Room Air Conditioner Branch Circuit Calculator

Branch circuit for a cord-and-plug room air conditioner per NEC 440.62: the 80% dedicated-circuit and 50% shared-circuit rules, and the minimum standard breaker.

Motor Overload Protection Calculator

Running-overload relay for a motor per NEC 430.32: 125% or 115% of nameplate full-load current, with the 430.32(C) increase to 140% or 130%.

Motor & HVAC Disconnect Sizing Calculator

Minimum disconnect ampere rating for a motor (NEC 430.110) or an A/C compressor (NEC 440.12): 115% of the table full-load current, or of the greater of RLA or BCSC.

Motor & A/C Equipment Disconnect Location Calculator

Where the disconnect has to go per NEC 440.14 (A/C) and 430.102(B) (motor): within sight (visible and within 50 ft), readily accessible, and the lockable exception.

Motor Full-Load Current Calculator

Look up motor full-load current from NEC Table 430.248/430.250 by horsepower and voltage (430.6(A)(1)), with the 430.22 branch-circuit conductor minimum ampacity.

Multi-Motor Feeder Calculator

Size a feeder for a group of motors per NEC 430.24 (125% of the largest motor FLC plus the other motors) and 430.62(A) (largest branch device plus the other FLCs, rounded down).

Several Motors on One Branch Circuit Calculator

Put several motors on one branch circuit per NEC 430.53: the (A) small-motor allowance (each 1 hp and 6 A or less), the (B) smallest-motor device, and the (C) group-installation device.

Feeder Tap Conductor Size Calculator

Size a feeder tap conductor under the NEC 240.21(B) 10-foot and 25-foot tap rules: required ampacity (1/10 or 1/3 of the feeder OCPD) and the smallest Table 310.16 conductor.

Transformer Secondary Conductor Calculator

Size a transformer secondary conductor under the NEC 240.21(C) rules: the reflected primary OCPD, the 10-foot and 25-foot secondary tap rules, and the smallest Table 310.16 conductor.

Generator Conductor Size Calculator

Size generator output conductors under the NEC 445.13(A) 115%-of-nameplate rule: nameplate current from kVA and the smallest Table 310.16 copper or aluminum wire.

Welder Circuit Calculator

Size a single arc welder branch circuit per NEC Article 630: the Table 630.11(A) duty-cycle-adjusted conductor from Table 310.16 and the 630.12 200% overcurrent device.

Group Welder Feeder Demand Calculator

Size a feeder to a group of arc welders per NEC 630.11(B): the 100/85/70/60% diversity on each welder’s 630.11(A) current, the Table 310.16 conductor, and the 630.12(B) feeder OCPD.

Capacitor Conductor & OCPD Calculator

Size power-capacitor circuit conductors per NEC 460.8(A): 135% of the rated capacitor current (from kVAR or entered directly) and the smallest Table 310.16 copper or aluminum wire.

Water Heater Circuit Calculator

Size an electric water heater branch circuit per NEC 422.13: the 125% continuous-load minimum breaker and conductor, plus the 422.11(E) 150% breaker maximum window.

Space-Heating Circuit Calculator

Size a fixed electric space-heating branch circuit (baseboard, unit heater, furnace) per NEC 424.3(B): 125% of the heater plus associated motor, with the 424.22(B) 48 A/60 A subdivision flag.

Range & Cooking Appliance Branch Circuit Calculator

Minimum branch-circuit rating for a household range, wall oven, or cooktop per NEC 210.19(A)(3): the 40 A range floor, the Table 220.55 demand basis, and the tap and neutral allowances.

Fire Pump Supply Conductor Calculator

Size fire pump supply conductors per NEC 695.6(B)(1): 125% of the fire pump plus jockey pump motor FLC, 100% of accessory load, and the smallest Table 310.16 copper or aluminum wire.

Service Disconnect Number & Rating Calculator

How many service disconnects the 2020 NEC allows and the minimum rating: the 230.71 single-disconnect change, the 230.79 floors (15/30/100/60 A), and the 230.80 combined rating.

Panelboard Overcurrent Protection Calculator

Check whether a breaker or fuse may protect a panelboard per NEC 408.36 (rated not greater than the panel) and find the largest permitted device, rounded down to a 240.6(A) standard.

Receptacle Rating & Branch-Circuit Load Calculator

Which receptacle a branch circuit may carry and how much load it may serve per NEC 210.21(B) and 210.23: permitted receptacle ratings, the Table 210.21(B)(2) maximum, and the 80%/50% limits.

Electrical Load Calculator

Dwelling service load per NEC 220.82 (optional method): floor area, appliances, and HVAC in; calculated amps and standard service size out.

Existing Dwelling Load Calculator

Existing dwelling addition per NEC 220.83: check whether an existing service can carry an added load, with the 8 kVA/40% split and the 220.60 noncoincident larger-of-HVAC rule.

Existing Load by Metered Demand Calculator

Existing load from measured demand per NEC 220.87: recorded maximum demand at 125% plus the new load, checked against the feeder ampacity or service rating, with the spare-capacity figure.

Multifamily Dwelling Load Calculator

Apartment building feeder and service load per the NEC 220.84 optional method: per-unit connected load at 100% nameplate, the Table 220.84 demand factor by unit count, and house loads added after.

Two-Family Dwelling Load Calculator

Duplex feeder and service load per NEC 220.85: the Article 220 Part III standard calculation for the two units run against the 220.84 optional method for three identical units, lesser governs.

Residential Electrical Load Calculator

Dwelling service load by the NEC Article 220 standard method: category-by-category demand factors (Tables 220.42/220.54/220.55, noncoincident HVAC, largest-motor adder).

Mobile Home Electrical Load Calculator

Single mobile or manufactured home supply per NEC 550.18: lighting on the home’s outside dimensions, Table 220.55 range, 220.54 dryer, noncoincident HVAC, and the 100 A minimum service (550.32(C)).

Commercial Load Calculator

Non-dwelling load per NEC 220 Part III: general lighting by occupancy (Table 220.12), receptacle, kitchen, and show-window loads to a service size.

Service Size Calculator

From a known load: minimum service disconnect (NEC 230.79), service-entrance conductor (230.42, Table 310.16), and grounding electrode conductor (Table 250.66) with the 250.66(A)/(B) caps.

Range / Cooktop Demand Load Calculator

Household cooking demand per NEC Table 220.55 Column C: one or more identical ranges, the Note 1 step over 12 kW, and the Note 4 branch-circuit cases for ranges, ovens, and cooktops.

Electric Dryer Demand Load Calculator

Household electric clothes dryer demand per NEC 220.54: the 5000 VA (or nameplate) per-dryer minimum and the Table 220.54 multi-dryer demand factors, with demand amps at 240 V.

Commercial Kitchen Equipment Demand Calculator

Commercial kitchen equipment demand per NEC Table 220.56: the demand factor by unit count plus the two-largest-loads floor made explicit, with demand kVA, kW, and amps.

Fixed Appliance Demand Load Calculator

Dwelling fastened-in-place appliance demand per NEC 220.53: the 75% demand factor for four or more appliances (100% otherwise), with the connected load and demand amps.

Commercial Receptacle Load Calculator

Non-dwelling receptacle load per NEC 220.14(I) and Table 220.44: 180 VA per strap, first 10 kVA at 100% and the rest at 50%, plus the 220.14(K) office 1 VA/ft² floor.

Neutral Load Calculator

Feeder and service neutral load per NEC 220.61: the maximum unbalance with the range and dryer 70% reduction, the over-200 A 70% demand factor, and the nonlinear no-reduction rule.

Minimum Branch Circuits Calculator

Minimum dwelling branch circuits per NEC 210.11: general-purpose circuits from the 3 VA/ft² general lighting load plus the required small-appliance, laundry, bathroom, and garage circuits.

Receptacle Spacing Calculator

Minimum dwelling receptacles per NEC 210.52: the 6 ft / 12 ft wall rule (210.52(A)) and the 24 in / 4 ft kitchen countertop rule (210.52(C)(1)), with the count per run.

Show Window & Sign Lighting Load Calculator

Show-window and sign loads per NEC 220.43(A)/220.14(G) and 220.14(F): 200 VA per linear foot of show window plus 1200 VA per required sign circuit, with the 125% continuous figure and amps.

Multi-Outlet Assembly Load Calculator

Fixed multioutlet assembly load per NEC 220.14(H): 180 VA per 5 ft where appliances are unlikely to run at once, or per 1 ft where likely, with the connected load and amps.

Track Lighting Load Calculator

Track lighting load per NEC 220.43(B): 150 VA per 2 ft of lighting track (or fraction thereof) at 100% in other-than-dwelling occupancies, with the 125% continuous figure and amps.

Receptacles Per Circuit Calculator

How many receptacles on a branch circuit: NEC 220.14(I) 180 VA per strap caps a 20 A circuit at 13 and a 15 A at 10 in non-dwellings, while dwelling units have no NEC limit.

Equipment Grounding Conductor Size Calculator

Minimum equipment grounding conductor from the OCPD rating per NEC Table 250.122, with the 250.122(B) proportional upsize for voltage-drop conductors and the 250.122(F) parallel-raceway rule.

Grounding Electrode Conductor Size Calculator

Minimum grounding electrode conductor from the service conductor size per NEC Table 250.66, with the 250.66(A) ground-rod and 250.66(B) concrete-encased caps and parallel equivalent-area handling.

Bonding Jumper Size Calculator

Minimum main, system, or supply-side bonding jumper and grounded conductor from the phase conductor per NEC Table 250.102(C)(1), including the Note 1 12.5% rule above 1100 kcmil and parallel equivalent-area handling.

Metal Water Pipe & Structural Metal Bonding Calculator

Bonding jumper for metal water pipe, gas pipe, or structural steel per NEC 250.104: Table 250.102(C)(1) with the 3/0 Cu / 250 kcmil Al water-pipe cap, Table 250.122 off the energizing OCPD for other piping, and the uncapped table for structural metal.

Ground Rod Resistance & Supplemental Rule Calculator

Whether a single rod, pipe, or plate electrode needs a supplemental electrode per NEC 250.53(A)(2): the 25-ohm exception, the unmeasured default, and the 250.53(A)(3) 6 ft spacing between two electrodes.

Separate Structure Grounding & Bonding Calculator

Grounding and bonding for a detached garage, shed, or outbuilding fed by a feeder or branch circuit per NEC 250.32: when a grounding electrode is required, when to run an equipment grounding conductor, and when the neutral is isolated at the structure.

Intersystem Bonding Termination Calculator

Whether an intersystem bonding termination for communications systems meets NEC 250.94: the three-terminal minimum, accessibility, enclosure clearance, the 6 AWG copper bond, and the listing requirement, at the service or a structure disconnect.

Solar PV Wire Size Calculator

PV source and output circuit conductors and fuses per NEC 690.8 and 690.9: 125% maximum current from Isc, the larger of the two 690.8(B) paths on Table 310.16, and the standard OCPD rating.

Solar 120% Rule Calculator

Load-side PV and storage interconnection per NEC 705.12(B)(3): the sum method and the 120% rule tested from 125% of the source output current, with the maximum source and largest standard backfed OCPD a busbar allows.

Working Space Clearance Calculator

Required working space in front of equipment 600 V or less per NEC 110.26(A): the depth from Table 110.26(A)(1) by Condition and voltage to ground, plus the 30 in width and 6.5 ft headroom.

Working Space Entrance & Egress Calculator

Entrance and egress for a working space per NEC 110.26(C): when equipment rated 1200 A or more and over 6 ft wide needs an exit at each end, the 24 in by 6.5 ft minimum opening, and the 800 A personnel-door panic-hardware rule.

Overhead Conductor Clearance Calculator

Minimum vertical clearance of an overhead service drop or feeder per NEC 230.24 and 225.18: 10/12/15/18 ft over sidewalks, driveways, and streets by voltage to ground, plus 24.5 ft over rails and 8 ft above roofs.

Dedicated Equipment Space Calculator

Dedicated equipment space above a switchboard, panelboard, or MCC per NEC 110.26(E): 6 ft above the equipment, or up to the structural ceiling indoors, kept clear of piping and ducts.

Conductor Clearance From Buildings Calculator

Clearance of overhead conductors from buildings per NEC 230.9 and 225.19: 3 ft from openable windows, doors, porches, signs, and walls for a service drop or outside feeder, with the fixed-window and above-window carve-outs.

Swimming Pool & Spa Equipment Clearance Calculator

Pool and spa equipment clearances per NEC 680.22 and 680.43: receptacles 6 to 20 ft from the water (10 ft for an indoor spa), luminaires 12 ft above, and switches 5 ft back, with a compliance check on a measured placement.

Swimming Pool & Spa Equipotential Bonding Calculator

Pool and spa equipotential bonding per NEC 680.26: which parts must be bonded, the 8 AWG solid copper conductor, the 3 ft perimeter surface, and the 5 ft horizontal by 12 ft vertical zone for nearby fixed metal parts.

Pool & Spa Equipment Maintenance Disconnect Calculator

Where the maintenance disconnecting means for pool and spa equipment goes per NEC 680.12: readily accessible, within sight (visible and within 50 ft), and at least 5 ft from the water unless a permanent barrier intervenes, with a compliance check.

Swimming Pool Underwater Luminaire Requirement Calculator

Underwater pool luminaires per NEC 680.23: the 150 V limit between conductors, when the branch circuit must be GFCI protected (above the 15 V AC / 30 V DC contact limit), and the 18 in minimum lens depth below the water (4 in absolute floor).

Bathtub & Shower Zone Clearance Calculator

Bathtub and shower zone per NEC 406.9(C) and 410.10(D): no receptacles or hanging luminaires within 3 ft horizontally and 8 ft vertically of the rim, plus the damp/wet listing for lights over the tub or shower.

Hydromassage Bathtub Receptacle & GFCI Calculator

Hydromassage (whirlpool) tub compliance per NEC 680.71/680.73/680.74: the readily accessible GFCI and individual branch circuit, the 6 ft / 125 V / 30 A nearby-receptacle GFCI rule, the 12 in service-opening rule, and the 8 AWG solid copper bond, with a compliance verdict.

Clothes Closet Luminaire Clearance Calculator

Clothes closet light rules per NEC 410.16: which luminaires are permitted, the 12 in or 6 in clearance from the storage space by type, and the 24 in / 12 in / 6 ft storage-space envelope the clearance is measured to.

Recessed Luminaire Clearance Calculator

Recessed can-light clearances per NEC 410.116: 1/2 in from combustibles and 3 in from thermal insulation (none above) for a non-Type IC fixture, versus the Type IC contact allowance, with a compliance verdict.

Tamper-Resistant & Weather-Resistant Receptacle Calculator

Where a receptacle must be tamper-resistant (NEC 406.12 dwellings, guest rooms, child care, schools, medical offices, assembly, dorms) or weather-resistant (NEC 406.9 damp and wet locations), with the four 406.12 exceptions and the extra-duty cover rule.

Receptacle Replacement Requirement Calculator

What a replacement receptacle must be under NEC 406.4(D): grounding type where a ground exists, the three options where none does (incl. the GFCI "No Equipment Ground" and two-prong cases), plus GFCI (210.8), AFCI (210.12), tamper-resistant (406.12), and weather-resistant (406.9) carried onto the new device.

Receptacle Mounting Position Calculator

Where and how a receptacle may be mounted under NEC 2020 406.5: the 406.5(G) face-up rules for countertops and work surfaces (406.5(G)(1), listed assembly only) and the area below a sink (406.5(G)(2), new in 2020), plus the 406.5(A)/(B) and 314.20 flush vs set-back box rules and the 406.5(D) face position.

Dwelling Lighting Outlet Requirements Calculator

Where a dwelling lighting outlet is required per NEC 210.70(A): the wall switch-controlled outlet in habitable rooms and baths (with the kitchen/bathroom exclusion), hallways, garages, and outdoor entrances, plus the six-riser stairway switching rule and the storage/equipment-space condition.

Dwelling Required Receptacle Outlets Calculator

Where a dwelling receptacle outlet is required per NEC 210.52 and the minimum count: kitchen small-appliance circuits, countertops, bathrooms (3 ft of each basin), outdoor, laundry, garages (one per vehicle bay), basements, hallways 10 ft or more, and foyers over 60 sq ft.

HVAC & Service Equipment Service Receptacle Calculator

Where a 125 V, 15/20 A service receptacle is required per NEC 210.63: within 25 ft and on the same level of HVAC and refrigeration equipment (210.63(A)), and in the same room or area as indoor service equipment and 110.26(E) dedicated-space equipment (210.63(B)), with the load-side and evaporative-cooler rules.

Snap Switch Mounting Height & Grouping Calculator

Switch and breaker accessibility per NEC 404.8: the 6 ft 7 in (2.0 m) maximum handle height with the busway, adjacent-equipment, and hookstick exceptions (404.8(A)), and the 300 V limit on the voltage between adjacent ganged devices unless an identified barrier is installed (404.8(B)).

Emergency Disconnect Requirement Calculator

The NEC 230.85 emergency disconnect for one- and two-family dwellings: the readily accessible outdoor location, the grouping rule for more than one disconnect, and the three marking labels for a service, meter, or other supply-side disconnect, with a compliance check.

Appliance Disconnecting Means Calculator

What serves as the disconnecting means for an appliance per NEC 422 Part III: the branch breaker at or below 300 VA / 1/8 hp (422.31(A)), a switch within sight or lockable above that (422.31(B)/(C)), an accessible plug (422.33), and the unit-switch allowance (422.34), with a compliance check.

Sign & Outline Lighting Outlet Requirement Calculator

When the NEC requires a sign/outline lighting outlet per 600.5(A): one outlet at each pedestrian-accessible entrance to each tenant space, a dedicated branch circuit rated at least 20 A, the 600.5(B) rating ceiling (20 A non-neon / 30 A neon), and the 1200 VA minimum computed load per required circuit (220.14(F)).

Show Window Receptacle Outlet Calculator

How many receptacle outlets a show window requires per NEC 210.62: one 125 V, 15 or 20 A receptacle within 18 in of the top for each 12 linear feet or major fraction (6 ft or more) of show window width, measured at the maximum width. The receptacle-count sibling of the Show Window & Sign Lighting Load tool.

Service Drop Point of Attachment Height Calculator

The minimum point-of-attachment height for an overhead service drop per NEC 230.26: the 10 ft floor above finished grade and the higher 230.24(B) span clearance that governs over a driveway (12 ft) or a street or truck-traffic area (18 ft), with a compliance check.

Service Disconnect Grouping & Load Marking Calculator

The NEC 230.72 / 230.70 installation rules for the service disconnecting means: grouping the two to six disconnects (230.72(A)), the service-disconnect (230.70(B)) and load-served (230.72(A)) markings, 230.70(C) suitability, and the 230.72(B) remote rule for fire-pump and standby disconnects, with a compliance check.

Separate Structure Disconnecting Means Calculator

The disconnecting means for a detached garage, shed, or outbuilding fed by a feeder or branch circuit per NEC 225.31/225.32/225.33: whether a disconnect is required, the readily-accessible nearest-the-entrance location rule with its four exceptions, and the six-disconnect maximum (single enclosure still permitted, unlike the service rule), with a compliance check.

Overcurrent Device Location & Accessibility Calculator

Where a panel, breaker, or fused switch may go under NEC 240.24: the 6 ft 7 in (2.0 m) maximum handle height and readily accessible rule (240.24(A)), each occupant's access (240.24(B)), and the physical-damage, clothes-closet, bathroom, and over-the-stairs prohibitions (240.24(C) through (F)), with a compliance check.

Guest Room / Guest Suite Receptacle Outlets Calculator

How many receptacle outlets a hotel, motel, or dormitory guest room or guest suite requires per NEC 210.60: the 210.52(A) 6 ft / 12 ft wall count, the 210.52(D) bathroom basin receptacle, and the 210.60(B) two-readily-accessible floor, with the behind-the-bed guard and permanent-cooking (all of 210.52) rules.