kW to HP Conversion: Kilowatts to Horsepower Explained

Quick Answer — TL;DR

To convert kilowatts to horsepower, multiply by the exact type-specific factor: 1 kW = 1.34102 mechanical HP (US/SAE), = 1.35962 metric HP (PS, DIN), = 1.34048 electrical HP. Example: 100 kW = 134.1 HP (mechanical), 136.0 PS. For HP→kW, divide. This guide explains definitions, 5 examples, costly mistakes, and FAQs with ISO/BIPM sources.

Power is measured differently around the world. Europe and most countries use kilowatts (kW) while the US and UK commonly use horsepower (HP). Converting between them is essential when comparing car specifications, machinery, and electrical motors.

The Conversion Formulas

1 kW = 1.341 mechanical HP
1 kW = 1.360 metric HP (PS)
1 kW = 1.340 electrical HP

To convert kW to HP: multiply by 1.341
To convert HP to kW: divide by 1.341

Common Power Conversions

50 kW = 67 HP (typical small car)
75 kW = 101 HP (compact car)
100 kW = 134 HP (mid-size car)
150 kW = 201 HP (performance car)
200 kW = 268 HP (sports car)
300 kW = 402 HP (luxury performance)
1 MW (1000 kW) = 1341 HP (heavy machinery)

Different Types of Horsepower

Mechanical horsepower (HP) is the US standard, used for car engines. Metric horsepower (PS) is used in Europe — 1 PS = 0.986 HP. Electrical horsepower is used for motors. The differences are small but can matter in precise engineering. Use our power converter above for accurate results.

Why kW is the Global Standard

The kilowatt is the SI unit for power and is used globally in science, engineering, and electrical applications. While car enthusiasts may prefer horsepower, kW provides a universal standard that eliminates confusion between different HP definitions.

Exact Factors, Definitions & Sources

Power is energy per time: 1 watt = 1 joule/second (BIPM SI). 1 kW = 1000 W exactly. Horsepower definitions: Mechanical (imperial) HP = 550 ft·lbf/s = 745.699872 W exactly (NIST), so 1 kW = 1000/745.699872 = 1.34102209 HP mechanical. Metric horsepower (PS, Pferdestärke) = 75 kgf·m/s = 735.49875 W exactly (DIN 66036), so 1 kW = 1.35962162 PS. Electrical HP = 746 W exactly (IEEE), so 1 kW = 1.34048257 electrical HP. Boiler HP (9812 W) is obsolete for engines. ISO 80000-4 standardizes power units; BIPM defines watt via kg·m²·s⁻³.

Sources: BIPM SI Brochure 9th ed. (watt definition), NIST SP 811 Appendix B8 (HP conversion factors), ISO 80000-4:2019 (mechanics), SAE J1349 for automotive HP correction, DIN 66036 for PS. Always state which HP you mean; 1 PS = 0.98632 HP mechanical — a 1.4% difference that matters at 300 kW.

Worked Examples (5-step table)

Worked examples — see the calculation shown step by step:

• Example 1 — Compact car: 75 kW → HP mech: 75×1.34102=100.58 HP; → PS: 75×1.35962=101.97 PS. Brochures in Germany quote PS, in US quote HP.
• Example 2 — Performance car: 220 kW → mech HP: 220×1.34102=295.0 HP; → PS=299.1 PS. Claiming 300 PS is 221 kW, not 220.
• Example 3 — Truck: 400 kW → HP: 400×1.34102=536.4 HP. Using electrical HP (×1.34048) gives 536.2 HP — similar but not identical for spec sheets.
• Example 4 — Reverse: 150 HP mech → kW: 150÷1.34102=111.85 kW. If you mistakenly divide by 1.36, you get 110.3 kW — 1.5 kW low.
• Example 5 — Electric motor: 11 kW home charger (15 HP electrical) delivers ~7 kW to battery after losses; converting nameplate PS without efficiency misstates real power.

Common Mistakes and How to Fix Them

• Mistake: Using 1 kW≈1.34 HP for all contexts. Fix: For EU cars, use 1.35962 PS; for US SAE net HP, use 1.34102; for motors, 1.34048. Specify in writing.
• Mistake: Confusing kW (power) with kWh (energy). Fix: kW is rate, kWh is total. 100 kW for 2 hours = 200 kWh. Do not convert kWh to HP.
• Mistake: Ignoring correction standards (SAE vs. DIN). Fix: SAE J1349 net HP and DIN 70020 PS use different temperature/pressure corrections. Compare corrected values only.
• Mistake: Rounding too early. Fix: Keep 5 significant digits until final display. 100 kW = 134.102 HP; rounding to 134 is fine for ads, but engineering needs 134.1.

Frequently Asked Questions (FAQ)

What is the difference between HP, PS, and bhp?

HP (mechanical) = 745.70 W, PS (= hp metric) = 735.50 W, bhp (brake HP) is mechanical HP measured at the crank without drivetrain losses. 1 PS = 0.9863 HP, so a German car rated 200 PS makes 197.3 HP mechanical. Bhp vs. whp (wheel HP) differs by ~12–15% drivetrain loss. Always ask: which HP and where measured?

Why does Europe quote kW while the US quotes HP, and which is more accurate?

kW is the SI coherent unit (BIPM), avoiding multiple HP definitions. Europe's type-approval (EU) requires kW on registration documents, with PS as an allowed supplement. The US EPA/SAE still uses HP due to tradition, but electric vehicles are accelerating the shift to kW globally because battery and charger ratings are in kW/kWh.

How do I convert kW to HP for electric motors and why does efficiency matter?

Electrical HP uses 746 W (1.34048 per kW). However, motor nameplate kW is mechanical output; electrical input is higher due to efficiency (e.g., 90% efficient 10 kW output draws 11.1 kW). Do not convert input kW to HP without adjusting for efficiency, or you will overstate shaft HP.

How to Convert Power in 3 Steps

1. Step 1: Identify the HP type required: mechanical (US cars, SAE), metric PS (EU cars), or electrical (motors/machines). Select the factor above.
2. Step 2: Multiply kW by the factor (or divide HP by it). Use the converter above for instant, exact results — it handles all three HP types.
3. Step 3: Label the result clearly (e.g., '295 HP (SAE) / 299 PS') and double-check with a known anchor: 100 kW ≈ 134 HP ≈ 136 PS.

Try the Converter & Keep Reading

Try it yourself: open the Power Converter or Energy Converter on OmniConverter for instant, high-precision results. For deeper reading, see our understanding power unit conversion — it pairs perfectly with this guide.

Real-World Example: Comparing EV and Gasoline Power Ratings

A 150 kW electric motor advertises 201 HP mechanical (150×1.341), but wheel horsepower is lower after inverter and drivetrain losses (~8%). Gasoline engines quote crank horsepower without alternator or cooling fan losses (SAE net). When comparing an EV's 150 kW to a gasoline car's 200 HP, note that 200 HP = 149 kW mechanical — essentially equal at the crank, but the EV delivers peak torque from 0 RPM. Always compare the same measurement point (crank vs. wheel) and the same HP type.

Sources: BIPM SI Brochure 9th edition (2019), NIST SP 811 Guide for the Use of the SI, ISO 80000 series for quantities and units. All exact factors are per international agreement.