Power and engine units: compare quantities before the numbers

State the horsepower convention explicitly

NIST’s conversion table distinguishes mechanical horsepower, defined using 550 foot-pounds-force per second, from metric horsepower. The published factors are 745.6999 watts and 735.4988 watts respectively. Our tool uses PS for metric horsepower and labels the mechanical convention bhp for this comparison. An unqualified hp label is ambiguous until the source identifies its convention. Do not silently treat every horsepower label as PS or as mechanical horsepower.

Using the published factors in kilowatts, kW equals PS multiplied by 0.7354988, and kW equals mechanical bhp multiplied by 0.7456999. Reverse the calculation by dividing kW by the appropriate factor. To convert between the two horsepower conventions, first convert to kW and then divide by the destination factor. The tool retains those factors during calculation and rounds only the displayed results.

• PS to kW: multiply by 0.7354988.
• Mechanical bhp to kW: multiply by 0.7456999.
• kW to either horsepower convention: divide by that convention’s factor.

Use the example as arithmetic, not vehicle data

The homepage example converts 100 kW to approximately 135.96 PS and 134.10 bhp. It is deliberately not attached to a make, model, registration or photograph. A seller’s different rounded number may warrant checking the unit and source, but conversion alone cannot show whether their description is accurate. Keep the original figure next to your converted figure so the calculation remains auditable.

A mechanical horsepower unit does not remove differences between measurement methods or test conditions. Brake horsepower refers to a measurement context; changing units does not turn a wheel-output measurement into an engine-output measurement. Ask what was measured, how it was reported and whether the figure is a manufacturer rating or a later test. A remap claim needs its own evidence.

Keep capacity, torque and energy in separate rows

Engine displacement is a volume, not power. The prefix relationship means 1 litre equals 1,000 cubic centimetres, so a purely mathematical 1,500 cc example is 1.5 litres. That does not determine an engine’s output, fuel consumption or exact identity. Retain the detailed capacity figure from the document rather than replacing it with a rounded marketing engine name.

Torque and power are different quantities; a torque figure without the relevant operating information should not be converted as though it were horsepower. For electrified vehicles, keep kW and kWh distinct: kW describes power and kWh describes energy. Do not add separate motor maxima to invent a manufacturer combined-system rating. Ask for a source that explicitly describes the complete system and exact variant.

• Record the original quantity, unit and source together.
• Do not use conversion to fill an unknown factory specification.
• Reject blank, zero or negative power input rather than creating a plausible result. If a source omits its unit entirely, ask for clarification before entering a value; an attractive-looking conversion would conceal the uncertainty rather than resolve it.