Electrical Calculators

Home and building electrical wiring, load, and power calculators based on NEC references

Calculate electrical power (watts) from voltage and current, with optional power factor.

Calculate current draw (amps) from power and voltage, single or 3-phase.

Estimate voltage drop over a wire run using the NEC formula, by gauge and length.

Find the minimum copper THHN wire gauge for a given ampacity per NEC Table 310.16.

Look up the rated ampacity of a copper THHN wire gauge (NEC Table 310.16).

Determine minimum EMT conduit trade size from total conductor area per NEC Chapter 9.

Calculate required electrical box volume from conductors, devices, and grounds (NEC 314.16).

Find the correct circuit breaker size using the NEC 125% continuous-load rule.

Find the correct fuse size using the NEC 125% continuous-load rule.

Estimate total electrical panel demand load and amperage (simplified NEC 220.42 method).

Calculate power for a three-phase electrical system from line voltage and current.

Calculate power factor from real and apparent power, or from phase angle.

Calculate apparent power (VA) from voltage and current, single or 3-phase.

Convert voltage and current to kVA for single-phase or three-phase systems.

Convert mechanical horsepower to kilowatts using the exact conversion constant.

Calculate electric motor efficiency from mechanical output and electrical input power.