Electrical calculators

Wire size starts at the 75°C column of NEC 2023 Table 310.16, copper or aluminum. Ambient and bundling factors stay at 1 unless you enter them. A second size respects 240.4(D), which caps 14, 12, and 10 AWG even when the table ampacity is higher. Voltage drop reuses the Chapter 9 K method and names a size at or under 3%. That 3% is an informational note, not a rule that fails an inspection. Verify the result with the adopted code and an electrician.

Conduit fill uses Chapter 9 Table 1: 53% for one conductor, 31% for two, 40% for three or more, and 60% for a nipple 24 inches or shorter. Conductor areas are Table 5. Conduit areas are the 100% column of Table 4. When every wire is the same size, a fractional count of 0.8 or more rounds up, which is Note 7. Derating and box fill are separate problems.

Voltage drop is 2 × K × amps × one-way feet ÷ circular mils for single phase, and √3 instead of 2 for three phase. K is 12.9 for copper and 21.2 for aluminum. The 3% branch and 5% feeder figures are informational notes in 210.19(A) and 215.2(A).