Free · NEC 2020 referenced · No signup
Voltage drop, conductor sizing, ampacity, and conduit fill — fast, and cited to the National Electrical Code (NEC) by table and article. Every result is verified against Southwire. No email walls, no DIY hand-holding.
Values reference the table and article. The edition is stated on every tool — default NEC 2020.
Outputs are checked to within 1% of the industry reference calculator before a tool ships.
Works on your phone on the jobsite. No account, no email capture, no popups.
Single- and three-phase AC voltage drop. K-factor for conductors under #2 AWG, NEC Chapter 9 Table 9 AC resistance for #2 and larger. Flags the 3% branch / 5% combined recommendations.
Open calculatorSize conductors for load, distance, and a target voltage drop. Cross-checks against NEC ampacity tables and standard OCPD sizes.
Conductor ampacity with ambient temperature correction and adjustment for more than 3 current-carrying conductors per NEC Table 310.16 and 310.15.
Open calculatorVoltage drop for DC circuits — solar, marine, automotive — using DC resistance values from NEC Chapter 9, Table 8.
Open calculatorConductor fill for EMT and RMC against the 53% / 31% / 40% limits in NEC Chapter 9, Table 1.
Open calculatorMaximum same-size conductor counts from NEC 2020 Annex C for EMT, IMC, RMC, and PVC Schedule 40/80. THHN/THWN-2 and XHHW-2 by trade size. Printable.
Open calculatorEach calculator implements the relevant NEC formula or table directly and cites the table number and edition in code. NEC values come from NFPA 70 and cross-checked trade references — never guessed. Before a tool ships, its reference scenarios are checked against Southwire's calculator and must match within 1%.
Results are for reference only. Verify against the applicable adopted edition of the NEC and consult a licensed electrician for code compliance.