Wire reference charts and calculators

Charts and calculators built from the NEC tables they cite. Each page names its table so you can check it against the edition your jurisdiction uses.

• Wire ampacity chart (NEC Table 310.16)

  Copper and aluminum ampacity at 60, 75 and 90 C from NEC Table 310.16, 14 AWG to 1000 kcmil, with the 240.4(D) breaker limits on small wire.

• AWG wire size chart (NEC Chapter 9, Table 8)

  Circular mils, square millimeters and DC resistance per 1,000 ft for copper and aluminum, 18 AWG to 1000 kcmil, from NEC Chapter 9, Table 8.

• What the letters on building wire mean

  What T, H, HH, W, N, X, R and -2 mean on building wire, with the temperature and location ratings of common types from NEC Table 310.4(1).

• Ampacity calculator

  Allowable ampacity for copper or aluminum wire with NEC ambient temperature correction, more-than-three-conductor adjustment, terminal rating and 240.4(D) limits.

• Conduit fill calculator (THHN/THWN-2)

  How many THHN or THWN-2 conductors fit in EMT or Schedule 40 PVC, from NEC Chapter 9 Tables 1, 4 and 5, with the Note 7 rounding.

• Voltage drop calculator

  Voltage drop for copper and aluminum wire, single phase, three phase and DC, with the smallest size that meets your target.

• Battery cable size calculator

  Size battery and inverter cable by voltage drop for 12, 24 and 48 V DC systems, using NEC Chapter 9, Table 8 copper resistance.