Metric Horsepower
Symbol: PSGermany, France, Japan, Russia, Most of Continental Europe
¿Qué es un/una Metric Horsepower (PS)?
Formal Definition
The metric horsepower (symbol: PS from German Pferdestärke, meaning "horse strength") is a unit of power defined as exactly 75 kilogram-force meters per second (75 kgf·m/s). In SI units, one metric horsepower equals approximately 735.49875 watts or 0.73550 kilowatts. The metric horsepower was created to provide a metric-system equivalent of the imperial horsepower defined by James Watt.
The metric horsepower is used under various names and abbreviations across the world: PS in Germany and Scandinavia, CV (cheval-vapeur) in France, Spain, and Italy, pk (paardenkracht) in the Netherlands, and л.с. (лошадиная сила) in Russia. Despite these different labels, they all refer to the same value: 75 kgf·m/s ≈ 735.5 W.
Comparison with Imperial Horsepower
One metric horsepower is approximately 1.4% less than one imperial (mechanical) horsepower: 1 PS = 735.5 W versus 1 HP = 745.7 W. This means 1 HP ≈ 1.0139 PS. While the difference is small, it becomes noticeable for high-power engines: a 500 HP engine would be rated at approximately 507 PS. In practice, marketing departments sometimes blur the distinction, leading to confusion among consumers.
Etymology
German Origins
The term Pferdestärke (PS) literally translates to "horse strength" in German. It was adopted as part of the metrication of the original horsepower concept. The French equivalent, cheval-vapeur (CV), translates to "steam horse," preserving the connection to the steam engine era. The Russian лошадиная сила (л.с.) directly translates to "horse power" or "horse strength."
Standardization
The metric horsepower was standardized during the adoption of the metric system across continental Europe in the 19th century. Engineers needed a power unit compatible with metric measurements of force (kilogram-force) and velocity (meters per second). By defining one metric horsepower as the power required to lift 75 kilograms by one meter in one second, they created a round number in metric units that was close to Watt's original imperial definition.
Historia
Metrication of Power
The metric horsepower emerged in the mid-19th century as continental European countries adopted the metric system but needed to retain a familiar power unit for engineers and consumers. Germany, France, and other nations independently defined the metric horsepower, converging on the value of 75 kgf·m/s, which produced a unit close to Watt's imperial horsepower.
Automotive Standardization
Throughout the 20th century, the metric horsepower became standard in continental European automotive specifications. German DIN standards (Deutsches Institut für Normung) defined testing conditions for PS ratings. Japanese manufacturers also adopted PS, which remains the standard unit for engine power in the Japanese domestic market.
EU Transition to Kilowatts
In 1992, the European Union's Directive 80/181/EEC mandated that kilowatts become the primary unit of engine power in official documents. However, the directive allowed PS to be used alongside kW as a supplementary unit. In practice, European car advertisements and reviews continue to prominently feature PS figures, with kW often appearing in smaller print. The metric horsepower shows no sign of disappearing from European automotive culture despite decades of official preference for kilowatts.
Uso actual
European Automotive Market
The metric horsepower remains dominant in automotive discussions across continental Europe. German car manufacturers (BMW, Mercedes-Benz, Volkswagen, Audi, Porsche) specify engine power in PS in marketing materials. A Porsche 911 Carrera produces 385 PS (283 kW), and consumers discuss its performance in PS, not kW. French, Italian, Spanish, and Scandinavian markets similarly prefer PS/CV.
Japan and Asia
Japanese automakers use PS as the primary power unit for domestic specifications. Japan's light car (kei car) regulations limit engine power to 47 kW (64 PS), a threshold universally discussed in PS rather than kW.
Russia and CIS
In Russia and CIS countries, лошадиная сила (л.с.) — the metric horsepower — is the standard unit for vehicle power. Russian transport tax is calculated based on engine power in л.с., making it a financially significant measurement for every vehicle owner.
Insurance and Taxation
In several European countries and Russia, vehicle insurance premiums and taxes are calculated based on engine power in PS/CV/л.с. In France, the fiscal horsepower (CV fiscaux) is derived from engine specifications and determines annual registration tax. In Italy, the bollo auto (vehicle tax) is calculated per kW but often discussed in CV.
Everyday Use
Understanding Car Specifications
When reading European car reviews or specifications, PS is the standard power unit. To convert mentally: PS figures are roughly equal to HP figures — the 1.4% difference is negligible for practical purposes. A 200 PS car and a 200 HP car are essentially the same power level.
Tax and Insurance Planning
In Russia, knowing your car's power in л.с. is essential for calculating transport tax. For example, cars with engines up to 100 л.с. have the lowest tax rate, while those exceeding 250 л.с. pay the highest. This can influence car buying decisions — a car with 249 л.с. may be significantly cheaper to own than one with 251 л.с.
International Comparisons
Car enthusiasts frequently compare vehicles from different markets, requiring conversions between PS, HP, and kW. The quick rule: PS ≈ HP (within 1.4%), and to convert PS to kW, multiply by 0.7355. A 400 PS German sports car produces about 294 kW or 394 HP.
In Science & Industry
Engineering Standards
German DIN standards and Japanese JIS standards define engine testing procedures that report results in PS. These standards specify conditions such as ambient temperature, barometric pressure, and accessory load that affect measured power. DIN 70020 was the traditional German standard for engine power measurement, now largely superseded by EU regulation ECE R85.
Historical Research
The metric horsepower appears extensively in historical technical literature from continental Europe. Researchers studying the development of automotive, marine, and industrial engines must be familiar with PS ratings and their relationship to modern kW measurements.
Interesting Facts
The difference between PS and HP is only 1.4%, but for a 1,000-horsepower supercar, this translates to a discrepancy of about 14 units — enough to matter in marketing claims.
Japan's kei car regulation limiting engines to 64 PS (47 kW) has been in effect since 1990. Before that, the limit was 64 PS for turbo engines only; naturally aspirated engines were unlimited.
In France, the fiscal horsepower (CV fiscaux) used for taxation is not the same as real horsepower — it's a calculated figure based on engine displacement and CO₂ emissions that only loosely correlates with actual power.
The abbreviation PS appears on German driver's licenses (Führerschein) to denote the maximum power of vehicles the holder is licensed to drive.
The most powerful road-legal car ever sold in Germany, the Bugatti Chiron Super Sport 300+, produces 1,600 PS (1,176 kW). Its top speed exceeded 490 km/h.
Russia's transport tax system using л.с. creates interesting market dynamics: manufacturers sometimes deliberately limit engine power to stay just below tax thresholds.