Your car's spec sheet is full of numbers: 150 hp, 32 psi, 7.2 L/100km, 220 Nm. But what do they actually mean? And why does the same car have completely different numbers depending on which country you're in?
This is the complete guide to every measurement unit you'll encounter as a driver, car buyer, or gearhead — with conversion tables that actually make sense.
Horsepower vs Kilowatts vs PS: Engine Power Explained
Every car lists its power output. But the unit depends on where you are:
| Unit | Symbol | Used In | 1 Unit = |
|---|---|---|---|
| Mechanical horsepower | hp | USA, UK, Canada | 745.7 W |
| Metric horsepower | PS (Pferdestärke) | Germany, EU (older), Japan | 735.5 W |
| Kilowatt | kW | EU (modern), Australia, science | 1,000 W |
Common Power Conversions
| hp | PS | kW | Typical Vehicle |
|---|---|---|---|
| 100 hp | 101 PS | 74.6 kW | Small city car |
| 150 hp | 152 PS | 112 kW | Average sedan |
| 200 hp | 203 PS | 149 kW | Sporty sedan |
| 300 hp | 304 PS | 224 kW | Sports car |
| 400 hp | 406 PS | 298 kW | Muscle car / performance |
| 500 hp | 507 PS | 373 kW | Supercar territory |
| 700 hp | 710 PS | 522 kW | Hypercar |
| 1,000 hp | 1,014 PS | 746 kW | Bugatti Chiron class |
Quick conversion shortcuts:
- hp to kW: multiply by 0.746 (or roughly divide by 1.34)
- hp to PS: multiply by 1.014 (nearly identical, PS is about 1.4% less)
- kW to hp: multiply by 1.341
Why both hp and PS exist: James Watt defined horsepower in the 1780s to sell steam engines, comparing them to horses. German engineers later created the metric version (PS = Pferdestärke = "horse strength"). The EU officially switched to kilowatts, but most car ads still use PS because "150 PS" sounds more impressive than "110 kW."
EV note: Electric car power is always measured in kW because electric motors are rated in watts. But most manufacturers convert to hp/PS in their marketing because consumers understand it better. A Tesla Model 3 Long Range produces about 350 kW (469 hp).
Torque: Nm vs lb-ft
Torque is what pushes you back in your seat when you accelerate. Power is how fast it happens.
| Unit | Symbol | Used In |
|---|---|---|
| Newton-meter | Nm | EU, Asia, Australia |
| Pound-foot | lb-ft (or ft-lbs) | USA, UK |
Common Torque Conversions
| Nm | lb-ft | Typical Vehicle |
|---|---|---|
| 150 Nm | 111 lb-ft | Small car |
| 250 Nm | 184 lb-ft | Average sedan |
| 350 Nm | 258 lb-ft | Turbocharged sedan |
| 500 Nm | 369 lb-ft | Diesel truck / performance car |
| 700 Nm | 516 lb-ft | Heavy-duty truck |
| 1,000 Nm | 738 lb-ft | Electric SUV / sports truck |
Quick conversion: 1 Nm = 0.7376 lb-ft. Or roughly: divide Nm by 1.36 to get lb-ft.
Why torque matters for EVs: Electric motors produce maximum torque instantly (from 0 RPM), which is why a Tesla can outlaunch a Ferrari off the line despite having fewer hp. The torque numbers for EVs look enormous — a Tesla Model S Plaid makes 1,020 Nm.
Tire Pressure: PSI vs Bar vs kPa
Incorrect tire pressure wastes fuel, wears tires unevenly, and can be dangerous. But the recommended pressure is listed differently worldwide:
| Unit | Symbol | Used In |
|---|---|---|
| Pounds per square inch | psi | USA, UK, Canada |
| Bar | bar | EU, most of the world |
| Kilopascal | kPa | Australia, some Asian countries |
Tire Pressure Conversion Table
| psi | bar | kPa | Common Use |
|---|---|---|---|
| 26 psi | 1.8 bar | 179 kPa | Light car, comfort |
| 28 psi | 1.9 bar | 193 kPa | Economy cars |
| 30 psi | 2.1 bar | 207 kPa | Sedans (front) |
| 32 psi | 2.2 bar | 221 kPa | Most common recommendation |
| 34 psi | 2.3 bar | 234 kPa | Sedans (rear, loaded) |
| 36 psi | 2.5 bar | 248 kPa | SUVs, heavier vehicles |
| 40 psi | 2.8 bar | 276 kPa | Full load / towing |
| 44 psi | 3.0 bar | 303 kPa | Light trucks |
| 60 psi | 4.1 bar | 414 kPa | Heavy trucks |
| 80 psi | 5.5 bar | 552 kPa | Commercial vehicles |
Quick conversions:
- psi to bar: divide by 14.5 (or multiply by 0.069)
- psi to kPa: multiply by 6.895
- bar to psi: multiply by 14.5
Practical tip: Your correct tire pressure is on a sticker inside the driver's door frame (or in the owner's manual), NOT on the tire sidewall. The number on the tire is the maximum rated pressure, not the recommended one.
Fuel Economy: MPG vs L/100km vs km/L
This is the most confusing car conversion because the systems measure opposite things:
- MPG = higher is better (distance per unit of fuel)
- L/100km = lower is better (fuel per unit of distance)
- km/L = higher is better (distance per unit of fuel)
| MPG (US) | MPG (UK) | L/100km | km/L | Rating |
|---|---|---|---|---|
| 15 mpg | 18 mpg | 15.7 | 6.4 | Gas guzzler |
| 20 mpg | 24 mpg | 11.8 | 8.5 | Below average |
| 25 mpg | 30 mpg | 9.4 | 10.6 | Average |
| 30 mpg | 36 mpg | 7.8 | 12.8 | Good |
| 35 mpg | 42 mpg | 6.7 | 14.9 | Very good |
| 40 mpg | 48 mpg | 5.9 | 17.0 | Excellent |
| 50 mpg | 60 mpg | 4.7 | 21.3 | Hybrid territory |
| 60 mpg | 72 mpg | 3.9 | 25.5 | Plug-in hybrid |
Why US and UK MPG are different: A US gallon is 3.785 liters, but an Imperial (UK) gallon is 4.546 liters — 20% bigger. So a car that gets 30 MPG in the US would get 36 MPG in the UK. Same car, same fuel consumption, different number. Always check which gallon the spec sheet means.
Quick conversions:
- L/100km to US MPG: divide 235.21 by L/100km
- US MPG to L/100km: divide 235.21 by MPG
- UK MPG to US MPG: multiply by 0.832
- km/L to L/100km: divide 100 by km/L
The inversion problem: Going from 10 to 15 L/100km saves less fuel than going from 5 to 10 L/100km. Both are "5 L/100km differences," but the first saves 33% while the second saves 50%. This is why L/100km is actually more intuitive for comparing fuel costs than MPG.
Speed: km/h vs mph
| km/h | mph | Context |
|---|---|---|
| 30 km/h | 19 mph | School zone |
| 50 km/h | 31 mph | Urban areas (EU/Asia) |
| 60 km/h | 37 mph | Urban (some countries) |
| 80 km/h | 50 mph | Rural roads |
| 100 km/h | 62 mph | Highways (many countries) |
| 110 km/h | 68 mph | Highways (Canada, Asia) |
| 120 km/h | 75 mph | Highways (EU standard) |
| 130 km/h | 81 mph | Highways (France, Italy) |
| 140 km/h | 87 mph | Poland highways |
| No limit | No limit | German Autobahn (advisory 130) |
| 200 km/h | 124 mph | Most cars' top speed |
| 300 km/h | 186 mph | Supercar territory |
Quick conversion: multiply km/h by 0.621 to get mph. Or more simply: km/h × 5/8 ≈ mph.
For a complete country-by-country breakdown of speed limits, check our dedicated speed limits page.
Engine Displacement: Liters vs Cubic Centimeters vs Cubic Inches
Engine size is expressed differently depending on the market:
| Liters | cc | Cubic inches | Typical Use |
|---|---|---|---|
| 1.0 L | 1,000 cc | 61 ci | City car, turbo 3-cylinder |
| 1.5 L | 1,500 cc | 91 ci | Compact car |
| 2.0 L | 2,000 cc | 122 ci | Most popular sedan size |
| 2.5 L | 2,500 cc | 153 ci | Mid-size sedan/SUV |
| 3.0 L | 3,000 cc | 183 ci | Premium sedan, V6 |
| 4.0 L | 4,000 cc | 244 ci | Performance / V8 |
| 5.0 L | 5,000 cc | 305 ci | American V8, sports car |
| 6.2 L | 6,200 cc | 376 ci | American muscle, trucks |
| 8.0 L | 8,000 cc | 488 ci | Bugatti Chiron territory |
Conversion: 1 liter = 1,000 cc = 61.024 cubic inches.
Marketing vs reality: "2.0T" means a 2.0-liter turbocharged engine. Thanks to turbocharging, modern 2.0L engines can produce power that previously required 3.0L+ naturally aspirated engines. Don't judge by displacement alone.
Vehicle Weight: kg vs lbs vs Curb Weight vs GVWR
| Term | Meaning |
|---|---|
| Curb weight | Weight of the car with all fluids, no passengers or cargo |
| Gross Vehicle Weight Rating (GVWR) | Maximum safe total weight including passengers and cargo |
| Payload capacity | GVWR minus curb weight = what you can add |
| Towing capacity | Maximum weight the vehicle can pull |
Weight Conversion Quick Reference
| kg | lbs | Typical Vehicle |
|---|---|---|
| 1,000 kg | 2,205 lbs | Small city car |
| 1,300 kg | 2,866 lbs | Compact car |
| 1,500 kg | 3,307 lbs | Average sedan |
| 1,800 kg | 3,968 lbs | SUV |
| 2,000 kg | 4,409 lbs | Large SUV / truck |
| 2,200 kg | 4,850 lbs | Full-size truck |
| 2,500 kg | 5,512 lbs | Heavy-duty truck / electric SUV |
EV weight note: Electric vehicles are significantly heavier than their gas equivalents due to battery weight. A Tesla Model Y weighs about 1,980 kg vs a comparable Toyota RAV4 at 1,600 kg. This affects tire wear, braking distances, and road damage.
Dimensions: Wheelbase, Ground Clearance, and Trunk Space
Car dimensions use different units by region:
| Measurement | USA | EU / Rest of World |
|---|---|---|
| Length, width, height | inches | mm (millimeters) |
| Wheelbase | inches | mm |
| Ground clearance | inches | mm |
| Trunk/boot space | cubic feet | liters |
Trunk Space Conversion
| Liters | Cubic feet | Fits |
|---|---|---|
| 200 L | 7.1 ft³ | Couple of grocery bags |
| 350 L | 12.4 ft³ | Small sedan trunk |
| 500 L | 17.7 ft³ | Average sedan trunk |
| 700 L | 24.7 ft³ | Station wagon / SUV |
| 1,000 L | 35.3 ft³ | Large SUV (seats up) |
| 2,000 L | 70.6 ft³ | Large SUV (seats folded) |
Conversion: 1 liter = 0.0353 ft³. Or: divide liters by 28.3 to get cubic feet.
Distance: Kilometers vs Miles on Your Odometer
If you've ever bought an imported car or rented one abroad:
| km | miles | Context |
|---|---|---|
| 1 km | 0.621 mi | — |
| 10,000 km | 6,214 mi | Low mileage car |
| 50,000 km | 31,069 mi | Average 3-year-old car |
| 100,000 km | 62,137 mi | Warranty limit for many brands |
| 150,000 km | 93,206 mi | Higher mileage, still good |
| 200,000 km | 124,274 mi | High mileage |
| 300,000 km | 186,411 mi | Reliable brands (Toyota, Honda) |
Used car tip: When buying an imported car, always check whether the odometer reads km or miles. A "50,000 mile" car has traveled 80,467 km — not what you might expect from a "50,000" reading if you're used to kilometers.
Temperature: Your Dashboard Gauges
| Reading | °C | °F | Meaning |
|---|---|---|---|
| Cold engine | < 60°C | < 140°F | Don't rev hard yet |
| Normal operating | 90-105°C | 194-221°F | Everything is fine |
| Running hot | 110-120°C | 230-248°F | Watch closely |
| Overheating | > 120°C | > 248°F | Pull over immediately |
| Oil temperature (normal) | 100-110°C | 212-230°F | Optimal |
| Outside temp display | -40 to 50°C | -40 to 122°F | Same at -40! |
Fun fact: -40°C = -40°F. It's the only temperature where both scales meet.
Wheel and Tire Sizes Decoded
A tire marked 225/45 R17 means:
- 225 = tread width in millimeters
- 45 = sidewall height as a percentage of width (225 × 0.45 = 101.25 mm)
- R = radial construction
- 17 = wheel diameter in inches (yes, mixed units!)
Total tire diameter = (2 × sidewall height) + wheel diameter
= (2 × 101.25 mm) + (17 × 25.4 mm) = 202.5 mm + 431.8 mm = 634.3 mm ≈ 25 inches
Tires are one of the few places where metric and imperial are mixed in the same specification.
Why Every Country Uses Different Car Units
The short answer: history.
USA: Stuck with Imperial because their automotive industry predates the metric push. Engine displacement in liters (thanks to foreign imports), everything else in imperial.
UK: Officially metric since the 1960s, but drives in mph, measures fuel economy in MPG (Imperial gallons, which are different from US gallons), and buys tires in mixed metric/imperial. The most confusing car market on Earth.
EU: Fully metric. km/h, kW, Nm, L/100km, bar. Clean and consistent — except they still list engine power in PS alongside kW for marketing.
Japan: Metric (km/h, kW, kPa), but with the unique "kei car" regulations that limit displacement to 660cc and dimensions to specific millimeter limits.
Australia: Fully metric since 1974. kW, Nm, L/100km, kPa. One of the most consistent metric adopters.
The bottom line: if you're comparing cars across markets, you WILL need conversions. Bookmark this guide — or use our converter to get exact numbers for any unit pair.