Horsepower to Kilowatts Calculator
Engine power conversion between mechanical horsepower, metric horsepower, and kilowatts
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What this calculator computes
Horsepower-to-kilowatt conversion translates the imperial unit of mechanical power that dominates US automotive specifications into the SI unit that dominates European, Asian, and electric-vehicle ratings. The calculator handles three horsepower variants because the unit name conceals significant ambiguity: mechanical (or imperial) horsepower equals exactly 745.6999 watts and is the figure in US engine specifications, metric horsepower (sometimes labelled "PS" for the German Pferdestärke or "CV" for the French Cheval-Vapeur) equals exactly 735.49875 watts and appears on European and Japanese vehicle specs, and electrical horsepower equals exactly 746 watts and is used in motor-and-pump nameplate ratings. The 1.4% gap between mechanical and metric horsepower means a "200 hp" American engine and a "200 PS" European engine are not the same power output — the European figure is about 1.4% lower in absolute kW terms. The kilowatt is the SI unit and is preferred in modern EV ratings (Tesla, Porsche, BMW i-series), in industrial-motor nameplate specifications, and in European Union vehicle type-approval documentation. The calculator outputs all three horsepower variants alongside the kilowatt figure to handle whichever convention the source document uses. The conversion appears constantly in international auto journalism, motor-and-pump industrial procurement, and any context where US-customary engine ratings cross over with the metric power conventions used in the rest of the world's documentation.
Calculator
The formula
Formula
kW = mechanical hp × 0.7457 kW = metric hp × 0.7355
Worked example
When to use this calculator
Use this calculator when comparing US-spec engines against European or Japanese specs, when reading EV power ratings (which are typically in kW even in US markets) against ICE vehicle hp figures, or when sizing industrial motors and pumps where the nameplate convention varies between manufacturers. EV manufacturers including Tesla, Porsche, BMW, and Audi quote motor power in kW on US-market specifications, with the horsepower equivalent often appearing only as a marketing-secondary figure. The calculator is also useful for sanity-checking power claims that mix unit systems within a single specification, such as a US-published European-import review where the original 200 PS figure may have been incorrectly translated as 200 hp without the 1.4% adjustment. The calculator does not handle torque conversions, peak-vs-continuous power distinctions, or the difference between brake horsepower (engine-output) and effective horsepower (post-drivetrain-loss at the wheels).
Common input mistakes
- Treating metric horsepower (PS, CV) as identical to mechanical horsepower. The two units differ by 1.4%, with metric horsepower being smaller. A "200 PS" European engine is 197.3 mechanical hp or 147.1 kW, while a "200 hp" US engine is 200 mechanical hp or 149.1 kW — different power outputs despite the matching numeric figure.
- Confusing brake horsepower (bhp) with horsepower at the wheels. Brake horsepower is the engine-shaft power measured directly at the crankshaft, while wheel horsepower is the power delivered to the road after drivetrain losses (typically 10–15% lower than crankshaft power for rear-wheel-drive cars and 15–25% lower for all-wheel-drive). Comparing dyno-measured wheel hp against manufacturer-rated bhp without the drivetrain-loss adjustment understates engine output.
Frequently asked questions
How many kilowatts is 1 horsepower?
One mechanical horsepower equals exactly 0.7457 kilowatts (or more precisely 745.6999 watts), and one metric horsepower (PS) equals 0.7355 kW (735.5 watts). The difference traces back to the unit definitions: James Watt defined mechanical horsepower in the 1780s based on the work rate of brewery draught horses, while metric horsepower was defined later as the work rate equivalent to lifting 75 kg one metre per second.
Why do EVs use kilowatts instead of horsepower?
EV manufacturers and the SAE engineering community prefer kilowatts because the SI unit is universal across the global market and integrates cleanly with battery-pack capacity ratings (kWh) and charging-rate specifications (kW). Tesla, Porsche, BMW i-series, and most other modern EVs publish kW figures as the primary power specification, with the horsepower-equivalent appearing as a marketing-secondary figure for US audiences. The trend is toward kW-only documentation as the global EV market matures.
What is the difference between PS, CV, and hp?
PS (Pferdestärke, German) and CV (Cheval-Vapeur, French) are both metric horsepower at exactly 735.49875 watts, used interchangeably in European vehicle specifications. Mechanical horsepower (often labelled simply "hp" in US documents) is 745.6999 watts, about 1.4% larger than the metric variants. A "200 PS" European spec equals 197.3 hp in US units, with the small but consistent gap reflecting the different historical definitions.
How precise should hp-to-kW conversion be?
For automotive marketing comparisons, two decimal places of kilowatts is sufficient — a 460 hp engine becomes 343.0 kW, with the precision matching typical dyno-measurement repeatability. For type-approval submissions and emissions-regulation filings, regulators expect the precise multiplier (0.7457) and three or four decimals of output. For casual conversion in journalism or product reviews, rounding to whole kW or whole hp is fine because the engine power varies more than the conversion precision in real-world driving conditions.
How does horsepower at the wheels differ from the manufacturer rating?
Manufacturer-rated horsepower is measured at the engine crankshaft on a dynamometer with no drivetrain attached, while wheel horsepower is measured on a chassis dynamometer with the full drivetrain spinning the rollers. Drivetrain losses typically claim 10–15% of crankshaft power for rear-wheel-drive cars and 15–25% for all-wheel-drive, so a manufacturer-rated 460 hp at the crankshaft typically reads 380–415 hp at the wheels of a RWD muscle car. Aftermarket dyno claims usually quote wheel hp because that is what the chassis dyno measures directly.