Inputs and units
The tool includes 208, 230 and 460 V three-phase selections, plus two single-phase options. This page starts at 460 V three phase. Choose a listed horsepower and a starting-current multiplier. The multiplier is an illustrative estimate, not a prediction of a particular starter or drive.
How the calculation works
Running current = stored table value for horsepower and supply
Estimated starting current = running current × selected multiplier
Three-phase apparent power (kVA) = √3 × line volts × line amps / 1,000The module identifies its stored running values with NEC motor tables. Table full-load current and measured operating current serve different purposes. The displayed 125% conductor figure is a simplified calculation and cannot settle every conductor, overload or short-circuit protection requirement. Check the adopted code edition, motor type and applicable exceptions for the actual task.
Worked example
For the stored 5 hp, 460 V three-phase entry, the tool returns 7.6 A running. Selecting the 6× estimate gives 45.6 A before display rounding. Apparent power is √3 × 460 × 7.6 ÷ 1,000 = about 6.06 kVA. These numbers do not establish the actual current of a motor at partial load.
Assumptions and limits
The table covers a limited set of horsepower and supply values. It does not model arbitrary motor efficiency, power factor, load, speed or starting duration. A VFD’s input current is not the same as its motor-side output current, and the shared soft-start/VFD multiplier should not be treated as a drive specification. Use nameplate and manufacturer data for the particular equipment, and verify code requirements with the applicable edition.
References and calculation details
Page prepared September 18, 2026. Examples describe this calculator’s implementation; reference links do not imply independent certification.