GFCI Breaker Sizing Calculator
Pick the occupancy and location to see whether NEC 2020 210.8 requires GFCI protection, then get the standard 240.6(A) breaker and the minimum conductor for the load. The ampere rating of a GFCI breaker is identical to any other breaker; what changes is knowing where GFCI is mandated and whether the circuit needs a 1-pole or 2-pole device.
How to use this calculator
- Choose the occupancy: a dwelling unit falls under NEC 210.8(A); anything else falls under 210.8(B).
- Select the location. The tool returns whether GFCI protection is required and the exact 210.8 item, or tells you the location is not listed.
- Enter the load in amperes (or watts plus voltage), split into continuous (3+ hours) and noncontinuous portions, and set the circuit voltage so the tool reports 1-pole versus 2-pole.
- Set conductor material and conditions to get the minimum conductor. Read the notes for device type, pole configuration, and any 240.4(B)/(D) conductor interactions.
NEC reference
GFCI requirement is determined by NEC 2020 210.8: 210.8(A) for dwelling units (eleven listed locations) and 210.8(B) for other than dwelling units (twelve listed locations). The 2020 edition significantly expanded these lists over 2017. The breaker ampere rating follows the same rules as any breaker: NEC 210.20(A) (100% noncontinuous plus 125% continuous), rounded up to a 240.6(A) standard rating, with the conductor checked against the 240.4(D) small-conductor limits and 240.4(B) next-size-up flagged when used.
Results are for reference only. Verify against the applicable adopted edition of the NEC and consult a licensed electrician for code compliance.
NEC 2020 210.8(A) dwelling unit GFCI locations
All 125-volt through 250-volt receptacles supplied by single-phase branch circuits rated 150 volts or less to ground, in these locations:
| Item | Location |
|---|---|
| (A)(1) | Bathrooms |
| (A)(2) | Garages and accessory buildings (floor at or below grade) |
| (A)(3) | Outdoors |
| (A)(4) | Crawl spaces at or below grade level |
| (A)(5) | Basements (finished or unfinished) |
| (A)(6) | Kitchens (countertop receptacles) |
| (A)(7) | Within 6 ft of a sink |
| (A)(8) | Boathouses |
| (A)(9) | Within 6 ft of a bathtub or shower stall |
| (A)(10) | Laundry areas |
| (A)(11) | Indoor damp and wet locations |
NEC 2020 210.8(B) non-dwelling GFCI locations
All 125-volt through 250-volt receptacles on single-phase branch circuits 150 volts or less to ground and 50 amperes or less, and receptacles on three-phase branch circuits 150 volts or less to ground and 100 amperes or less, in these locations:
| Item | Location |
|---|---|
| (B)(1) | Bathrooms |
| (B)(2) | Kitchens or areas with a sink and food-prep or cooking provisions |
| (B)(3) | Rooftops |
| (B)(4) | Outdoors |
| (B)(5) | Within 6 ft of a sink |
| (B)(6) | Indoor damp and wet locations |
| (B)(7) | Locker rooms with associated showering facilities |
| (B)(8) | Garages, service bays, and similar areas |
| (B)(9) | Crawl spaces at or below grade level |
| (B)(10) | Unfinished areas of basements |
| (B)(11) | Laundry areas |
| (B)(12) | Within 6 ft of a bathtub or shower stall |
210.8 also carries additional subsections beyond receptacle locations: 210.8(C) crawl space lighting, 210.8(D) dishwasher branch circuits, 210.8(E) equipment requiring servicing, and 210.8(F) outdoor outlets. Special occupancies (pools and spas in Article 680, marinas in 555, and others) impose their own GFCI rules. This tool evaluates the 210.8(A) and 210.8(B) receptacle-location lists.
Sizing a GFCI breaker: same ampere math
A GFCI circuit breaker is an ordinary thermal-magnetic breaker with a ground-fault sensor added, so its ampere rating is chosen exactly like any breaker. Apply NEC 210.20(A): the device must be rated at least 100% of the noncontinuous load plus 125% of the continuous load, then round up to a standard rating from 240.6(A). The conductor is sized to the same requirement and checked against the 240.4(D) small-conductor caps (copper 14/12/10 AWG at 15/20/30 A) so the breaker can legally protect it.
GFCI circuit breakers are commonly stocked from 15 A through 60 A in both 1-pole (120 V) and 2-pole (120/240 V) versions. Above 60 A, a GFCI breaker may be special-order; GFCI protection at higher ratings is sometimes provided by a listed GFCI device, and equipment ground-fault protection (GFP, 30 mA and up) is a different device class that does not satisfy the personnel GFCI requirement.
Frequently asked questions
Where does the NEC require GFCI breakers?
NEC 210.8 lists the locations, split into 210.8(A) for dwelling units and 210.8(B) for everything else. Use the tool above to check a specific location and get the exact item number. Note that GFCI protection can be provided by a GFCI breaker or a GFCI receptacle; the code requires the protection, not a particular device.
Does a 240V circuit need a 2-pole GFCI breaker?
Yes. A 208 V or 240 V circuit uses a 2-pole GFCI breaker. Any shared neutral must terminate on the breaker neutral terminal so the ground-fault sensor reads all circuit conductors. A 120 V or 277 V line-to-neutral circuit uses a 1-pole GFCI breaker.
Is a GFCI breaker the same as an AFCI breaker?
No. A GFCI protects people from shock and is required by 210.8; an AFCI detects arcing to prevent fires and is required by 210.12. Dual-function breakers do both. This calculator handles the 210.8 GFCI requirement only. AFCI sizing is a separate topic.
Why doesn't this work for motors and AC units?
Motor branch circuits (Article 430) and HVAC equipment (Article 440) size protection differently, using the equipment nameplate MCA and MOP or the NEC 430 tables. The breaker half of this tool covers general-use loads, so feed motor and HVAC loads through the Motor Breaker Sizing Calculator or the nameplate instead.
Related calculators
- Breaker Size Calculator: general-use breaker and conductor sizing without the GFCI location check.
- Motor Breaker Sizing Calculator: motor branch-circuit protection per NEC Article 430.
- Wire Size Calculator: full conductor sizing with voltage drop and OCPD together.
- Wire Ampacity Calculator: derated ampacity of a specific conductor.
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