How the converter works
Every value is first converted to its SI base unit (metre, kilogram, pascal, joule, watt, kelvin…) and then to each target unit. Factors come from exact definitions where they exist: the international inch is exactly 25.4 mm, the pound exactly 0.45359237 kg and standard gravity exactly 9.80665 m/s², which fixes the kilogram-force and pound-force.
Notes on units that are easy to confuse
- Horsepower: “hp” here is mechanical horsepower (745.7 W). Metric horsepower (PS) is 735.5 W. Electrical motors are usually rated in kW.
- Gallons: the US gallon (3.785 L) and the imperial UK gallon (4.546 L) are different.
- Tons: tonne (1000 kg), US short ton (907.2 kg) and UK long ton (1016 kg) are different.
- Temperature: this converts temperature readings. A temperature difference of 1 °C equals 1 K and 1.8 °F.
- Calorie and BTU: the thermochemical calorie (4.184 J) and the International Table BTU (1055.056 J) are used.
- Pressure: values are absolute or gauge exactly as you enter them — the converter does not add atmospheric pressure.