You have kilowatts from a meter, datasheet, or drive display—now you need horsepower for a motor match or pump curve. This guide shows how to calculate horsepower from kilowatts step by step using the mechanical hp constant.
Benefits
- Single-step calc: HP = kW ÷ 0.7457.
- Worked examples from common motor and inverter kW ratings.
- Reverse check: kW = HP × 0.7457 before quoting equipment.
How it works
- Identify real power in kW—shaft, output, or measured load (not kVA).
- Divide by 0.7457 to calculate mechanical horsepower.
- Round to catalog hp steps (5, 7.5, 10, 15 hp) for procurement.
FAQ
How do I calculate horsepower from kilowatts?
HP = kW ÷ 0.7457. Example: 11.2 kW → 11.2 ÷ 0.7457 ≈ 15.02 hp—round to a 15 hp motor class. For 5.6 kW: 5.6 ÷ 0.7457 ≈ 7.51 hp, matching a standard 7.5 hp frame.
Can I calculate hp from three-phase kW?
Yes—when the kW value is already real power (not kVA), the same formula applies. A three-phase 460 V motor drawing 14 kW shaft-equivalent power is 14 ÷ 0.7457 ≈ 18.8 hp. Use measured or nameplate kW, not line voltage alone.
What if my kW includes motor losses?
Input electrical kW is higher than shaft hp/kW when efficiency is below 100%. To calculate shaft horsepower from electrical kW, multiply kW by motor efficiency first, then divide by 0.7457. Example: 10 kW electrical at 90% efficiency → 9 kW shaft → 12.07 hp.
Technical specifications
- HP = kW ÷ 0.7457 (mechanical).
- Shaft kW = electrical kW × efficiency (when needed).
- Standard NEMA hp steps: 1, 1.5, 2, 3, 5, 7.5, 10, 15, 20, 25, 30…
- Related: kw-to-hp-converter, convert-kilowatts-to-mechanical-horsepower.