Unit Converter
| Unit | Value |
|---|
Convert length, weight, temperature, volume, area, speed and data between metric and imperial units. Every unit in the category is converted at once, so you can read across.
Conversions worth memorising
| Metric | Imperial | Close enough |
|---|---|---|
| 1 kilometre | 0.621 miles | Multiply by 0.6 |
| 1 metre | 3.28 feet | A bit over 3 |
| 1 kilogram | 2.20 pounds | Double it |
| 1 litre | 0.264 US gallons | Quarter of a gallon |
| 0 °C | 32 °F | Double and add 30 |
The two-system problem
Three countries have not formally adopted the metric system, but imperial units persist far more widely than that suggests — aviation measures altitude in feet worldwide, screen sizes are in inches everywhere, and shipping runs on both. Mixed-unit projects are normal, and mixed-unit mistakes are expensive.
The most famous is the Mars Climate Orbiter, lost in 1999 because one team supplied thrust in pound-force seconds while the navigation software expected newton seconds. The lesson generalises: write the unit next to every number you record.
Frequently asked questions
Why is temperature converted differently from other units?
Length, weight and volume scales all start at zero, so converting is a single multiplication. Celsius and Fahrenheit have different zero points, so the conversion needs an offset as well as a factor: F = C × 9/5 + 32. Kelvin shares the Celsius degree size but starts at absolute zero, which is why you add 273.15 rather than multiplying.
Is a US gallon the same as a UK gallon?
No, and the gap is large. A US liquid gallon is 3.785 litres while an imperial gallon is 4.546 litres — about 20 percent more. The same split applies to pints, quarts and fluid ounces, which is why American and British recipes are not interchangeable by volume.
What is the difference between mass and weight?
Mass is how much matter something contains; weight is the force gravity exerts on that mass. Kilograms measure mass, newtons measure force. In everyday use on Earth the distinction rarely matters, which is why kilograms and pounds are used interchangeably for both — but on the Moon your mass is unchanged and your weight is a sixth.
How precise are these conversions?
The factors are exact by definition wherever a definition exists: one inch is exactly 25.4 millimetres, one pound is exactly 0.45359237 kilograms. Results are displayed to a sensible number of significant figures rather than the full floating-point expansion, so very large and very small values switch to scientific notation.
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