What is Metric Horsepower (PS)? PS vs HP Explained

If you read car specifications from different countries, you've likely noticed two different "horsepower" figures: HP and PS. While often used interchangeably, they are not exactly the same. This guide explains the difference.

Quick Answer (TL;DR)

• HP (Mechanical Horsepower): Used in US/UK. 1 HP = 745.7 Watts.
• PS (Metric Horsepower): Used in Europe/Asia. 1 PS = 735.5 Watts.
• The Difference: PS is about 1.4% smaller than HP.
• Conversion: 1 HP = 1.014 PS.

Example: A "300 PS" car actually has 296 HP.

Understanding the Units

What is PS (Pferdеstärke)?

PS stands for Pferdestärke, which is German for "horse strength." It is the standard unit for power in DIN (German) and JIS (Japanese) standards.

• Definition: The power needed to lift 75 kilograms by 1 meter in 1 second.
• Value: 1 PS = 735.49875 Watts.
• Also known as:
  • cv (cheval-vapeur) in France
  • ch (chevaux) in French car specs
  • pk (paardenkracht) in Netherlands

What is HP (Mechanical Horsepower)?

HP (often called Imperial or Mechanical Horsepower) was defined by James Watt.

• Definition: The power needed to lift 550 pounds by 1 foot in 1 second.
• Value: 1 HP = 745.69987 Watts.
• Used in: United States, United Kingdom, and former Commonwealth countries.

Why Do We Have Two Units?

It stems from the metric vs. imperial divide:

1. James Watt defined horsepower using imperial units (pounds, feet).
2. Europe wanted a similar unit but defined using metric units (kilograms, meters).
3. Because 1 kg ≠ 2.2 lbs exactly, and gravity varies slightly, the definitions drifted apart by about 1.4%.

How to Convert PS to HP

Since 1 PS is slightly smaller than 1 HP, the number in PS will always be higher than the number in HP for the same engine.

Conversion Formulas

PS to HP:

HP = PS × 0.9863

HP to PS:

PS = HP × 1.0139

Quick Reference Table

Real-World Confusion

Marketing departments often use the larger number (PS) without specifying, or mix them up.

Example: Bugatti Veyron

• Marketing: "1001 Horsepower!"
• Reality: It was 1001 PS.
• In US HP: 1001 × 0.986 = 987 HP.
• Still fast, but not quite 1000 HP!

Example: McLaren 720S

• The "720" stands for 720 PS.
• In US HP: 720 × 0.986 = 710 HP.

When to Use Which?

Use HP when:

• Talking about American cars (Ford, GM, Dodge)
• In the US or UK market
• Reading US magazines (Car and Driver, MotorTrend)

Use PS when:

• Talking about German cars (Porsche, BMW, Audi)
• Talking about Japanese cars (JDM specs)
• In Europe or Asia

Use kW (Kilowatts) when:

• You want to be scientifically accurate.
• kW is the only truly ambiguous international standard.
• Electric Vehicles (EVs) are increasingly rated solely in kW.

Frequently Asked Questions

Is bhp the same as HP?

Yes, "bhp" (brake horsepower) usually refers to mechanical HP (imperial) measured at the engine crankshaft.

Why do EVs use kW?

Electric motors are rated in Watts/kW electrically, so it makes sense to output mechanical power in kW too. It eliminates the HP/PS confusion entirely.

Does 1.4% really matter?

For a daily driver (150 HP), the difference is 2 HP—negligible. For a hypercar (1000 HP), the difference is 14 HP—enough to brag about, but rarely felt on the road.

Conclusion

Metric Horsepower (PS) and Mechanical Horsepower (HP) are almost the same, but PS is slightly smaller.

• Rule of Thumb: PS is always ~1.4% higher than HP.
• Easy Conversion: Subtract 1.4% from PS to get HP.

For precise conversions, use our tools:

• HP to kW Converter
• Power Unit Calculator

Last Updated: January 28, 2026
Reading Time: 6 minutes