Free · Physics models
Motor Output Horsepower to Current
Estimate DC or balanced AC motor input current from output power, efficiency and supply voltage.
- Formula & worked example
- Private in your browser
- No signup
Calculator inputs
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How to use this calculator
- Enter the known values in the units shown. Results update as you type.
- Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
- Use the worked example to check the method. Reset restores the starting fields.
Private by default
Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.
Formula and method
One electrical horsepower (746 W) of output at 100% efficiency and 100 V requires 7.46 A DC.
IDC = Pout/(Vη); IAC = Pout/(Vη PF), with the appropriate three-phase voltage factor.
Worked example
Enter these known values and leave the other values blank.
- Power (hp)
- 1 hp(E)
- Voltage (V)
- 100 V
- Efficiency (η)
- 100 %
- Amperage (amps)
- 7.46 A
Assumptions and limitations
- The default horsepower type is electrical horsepower, defined here as 746 W. Other horsepower selectors use their retained conventional conversions.
- Efficiency is strictly between zero and 100%; AC power factor is strictly positive and no greater than one.
- Use RMS AC voltage. Three-phase formulas assume a balanced load and distinguish line-to-line from line-to-neutral voltage.
- Enter known quantities and clear the unknown to use available inverse branches. Locks retain supplied values. Consistency messages cover fully visible equations; identities with hidden dependencies may require a manual consistency check. Preset values are illustrative approximations, and unit selectors preserve the underlying quantity.
Common questions
How do I solve for a different quantity?
Clear that quantity and supply enough independent known values. Some outputs are one-way or tied to a selected preset, so they cannot determine every input.
References
The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.