Unit Converter

Common conversions

1 inch = 2.54 cm exactly; 1 mile = 1.609344 km; 1 kg = 2.20462 lbs; 1 US gallon = 3.78541 liters; °F = °C × 9/5 + 32; 1 mph = 1.609344 km/h. All factors in this converter use the exact international definitions where they exist (the inch, pound and mile are defined exactly in metric terms), so results are as precise as your input.

Frequently asked questions

Which gallon does it use?

The US gallon (3.785411784 L). The UK imperial gallon (4.54609 L) is listed separately as "gallon (UK)".

Why do temperature conversions work differently?

Celsius, Fahrenheit and Kelvin scales have different zero points, not just different step sizes, so they convert with an offset formula rather than a simple multiplication — the tool handles this automatically.

How many decimal places are shown?

Up to 8 significant decimals, with trailing zeros trimmed — enough for engineering use without fake precision.