Updated November 2026 · free, works in your browser
Show the formula
Result = value × (factor of the source unit ÷ factor of the target unit). Every unit is defined exactly in a base unit: metre (m), kilogram (kg) or litre (L).
Length: 1 in = 0.0254 m, 1 ft = 0.3048 m, 1 yd = 0.9144 m, 1 mi = 1,609.344 m.
Weight: 1 oz = 0.028349523125 kg, 1 lb = 0.45359237 kg, 1 st = 6.35029318 kg, 1 US ton = 907.18474 kg.
Volume: 1 US fl oz = 0.0295735295625 L, 1 US cup = 0.2365882365 L, 1 US qt = 0.946352946 L, 1 US gal = 3.785411784 L.
To convert US units to metric, multiply the value by the exact conversion factor of the unit you start from: 1 inch is 2.54 centimetres, 1 mile is 1.609344 kilometres, 1 pound is 0.45359237 kilograms and 1 US gallon is 3.785411784 litres. The converter above does this instantly for length, weight and volume, in both directions.
How to use
- Choose what you want to measure: length, weight or volume.
- Pick the direction, from US units to metric or from metric to US units.
- Select the unit you are starting from, for example miles, pounds or gallons.
- Type the value. All matching units appear immediately below.
- Use the copy button to share a link that restores your exact conversion.
How it is calculated
Every unit is defined exactly in terms of a base unit: the metre for length, the kilogram for mass and the litre for volume. The converter first turns your value into the base unit and then divides by the factor of the target unit:
result = value × (factor of source unit ÷ factor of target unit)
Here "factor" means how many base units one unit contains, for example 1 mile = 1,609.344 m. These factors come from the international yard and pound agreement of 1959 and the definitions published by national standards bodies such as NIST. Results are rounded to four decimals for numbers between 1 and 1,000, to two decimals for larger numbers and to four significant digits for numbers below 1.
Common conversion factors
| US unit | Metric equivalent |
|---|---|
| 1 inch | 2.54 cm |
| 1 foot | 0.3048 m |
| 1 yard | 0.9144 m |
| 1 mile | 1.609344 km |
| 1 ounce | 28.3495 g |
| 1 pound | 0.453592 kg |
| 1 US fluid ounce | 29.5735 mL |
| 1 US gallon | 3.78541 L |
FAQ
Is a US gallon the same as a British gallon?
No. A US gallon is 3.785 litres, while an imperial (British) gallon is about 4.546 litres. This tool uses US liquid volumes, so do not use it for imperial gallons or pints.
What is the difference between a US ton and a metric tonne?
A US ton (short ton) is 2,000 pounds, or about 907 kilograms. A metric tonne is 1,000 kilograms, about 2,204.6 pounds. The converter lists both under their own names.
Why is a stone included?
The stone is a British unit of 14 pounds, about 6.35 kilograms, still used for body weight in the United Kingdom and Ireland, so it is handy next to the US units.
How many kilometres is a mile?
One mile is exactly 1.609344 kilometres. A quick mental shortcut is to multiply miles by 1.6, which is close enough for road signs.
Why do I see a message instead of a result?
The converter needs a number greater than zero and below one billion. Empty, zero, negative or non-numeric entries show a short hint instead of a result.
Whenever you travel to a country that uses a different measurement system, these conversions become part of everyday planning: road distances in miles, fuel sold by the gallon or litre, and luggage limits in pounds or kilograms. Converting them in advance helps you judge driving times, compare fuel costs and pack within airline allowances before you settle on where to stay.
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