Current Calculations

Find the current calculator that matches your available data. Use kW to amps when you know electrical real power, voltage and power factor. Use kVA or VA to amps when you already know apparent power; do not apply power factor a second time. A balanced three-phase calculation uses line-to-line voltage, while a single-phase calculation uses the voltage across the load. When starting from motor shaft horsepower, efficiency is also needed to estimate electrical input. Confirm whether a rating describes one phase, one winding or the entire load before entering it. The tools below provide formulas and examples for these different starting points. A calculated operating current is not the same as a motor starting current or an automatically approved breaker or conductor rating.

Current calculators by starting quantity

Choose the known power quantity, then supply the circuit voltage and configuration.

kW to amps — Start with electrical real power.

kVA to amps — Start with apparent power; match voltage to the selected winding or circuit.

VA to amps — Useful for lower-power transformers and supplies.

HP to amps — Distinguish motor shaft output from electrical input.

Three-phase current — Choose kW, HP or kVA with the assumptions shown in the tool.

Continue to wire ampacity — Use the current with the separate cable model.

Watts to amps — Start with electrical input watts or motor shaft output, compare voltages and save three cases with their power factor and efficiency assumptions.