Calculators · Reference

Automotive and engineering unit converter

Vehicle and machinery specifications mix metric and imperial units, and even within the metric world power is quoted in both kW and PS. This page converts the units you meet most often in specifications — power, torque, pressure, engine displacement and speed — showing every common unit at once, so you can compare figures from different countries directly.

Power: kW, hp and PS

Converts engine power between kilowatts, mechanical horsepower (hp, used in the US and UK) and metric horsepower (PS or cv, used across Europe). One PS is about 1.4% smaller than one hp.

Results
Kilowatts—kWSI unit used in official European data.
Mechanical horsepower—hp745.7 W; used in the US and UK.
Metric horsepower—PS735.5 W; used in Germany and much of Europe.

Formula
1 hp = 0.7457 kW
1 PS = 0.7355 kW

Torque: Nm, lb-ft and kgf·m

Converts torque between newton-metres, pound-feet and kilogram-force metres, which older Japanese and European specifications still use. Useful for comparing engine data and tightening torques.

Results
Newton-metres—NmSI unit of torque.
Pound-feet—lb-ftUsed in US specifications.
Kilogram-force metres—kgf·mFound in older specifications.

Formula
1 lb-ft = 1.3558 Nm
1 kgf·m = 9.8067 Nm

Pressure: bar, psi, kPa and atm

Converts tyre, boost, hydraulic and compressed-air pressures between the common units. Tyre and boost gauges read gauge pressure — pressure above atmospheric.

Results
Bar—barCommon in Europe for tyres and hydraulics.
Pounds per square inch—psiCommon in the US and UK.
Kilopascals—kPaSI unit, used on many tyre placards.
Standard atmospheres—atm1 atm = 1.01325 bar.

Formula
1 bar = 14.504 psi = 100 kPa

Engine displacement: cc, litres and cubic inches

Converts engine size between cubic centimetres, litres and cubic inches, the unit traditionally used for American V8s such as the 350 or 427.

Results
Cubic centimetres—ccAlso written cm³.
Litres—LUsually rounded to one decimal in model names.
Cubic inches—cu in1 cu in = 16.387 cc.

Formula
1 L = 1,000 cc
1 cu in = 16.387 cc

Speed: km/h, mph, m/s and knots

Converts speeds between the units used on roads, in engineering and on water. Boats and aircraft use knots — nautical miles per hour.

Results
Kilometres per hour—km/hRoad speed in most of the world.
Miles per hour—mphRoad speed in the US and UK.
Metres per second—m/sSI unit, used in physics and engineering.
Knots—kn1 knot = 1.852 km/h.

Formula
1 mph = 1.609 km/h
1 m/s = 3.6 km/h
1 knot = 1.852 km/h

Worked example: reading a European specification

  1. A car rated at 150 PS produces 150 × 0.7355 = 110.3 kW, or 148 hp.
  2. 350 Nm of torque is 258 lb-ft.
  3. A tyre pressure of 2.4 bar is about 35 psi, or 240 kPa.
  4. A 5.7-litre engine is 348 cubic inches — the famous “350”.

Common conversion factors

FromToMultiply by
kWhp1.341
kWPS1.360
Nmlb-ft0.7376
barpsi14.504
litrescubic inches61.024
km/hmph0.6214
kglb2.2046

Related

Torque, power and BMEP calculatorEngine displacement and bore/stroke calculatorBoost pressure and pressure ratio calculatorFuel economy converter and trip cost calculator

About these results

Results are theoretical estimates from standard engineering formulas. Real-world figures depend on conditions these formulas do not capture. Always follow the manufacturer's specifications for maintenance, loading and safety decisions.

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