Unit Conversion Calculator
Convert length, weight, temperature, volume, area and speed between metric, imperial and US customary units.
How to Use the Unit Conversion Calculator
Our Unit Conversion Calculator converts between metric, imperial and US customary units across six common categories: length, weight and mass, temperature, volume, area, and speed. Choose a category, enter a value, pick your “from” and “to” units, and the result updates instantly. Use the swap button to reverse the direction of any conversion in one click.
Common Unit Conversions
- Choose a category: Length, Weight & Mass, Temperature, Volume, Area, or Speed.
- Enter the value you want to convert.
- Select the from unit and the to unit.
- The converted result appears automatically, along with a quick-reference table of common conversions in that category.
- Use the swap button (⇆) to flip the from/to units and instantly see the conversion in reverse.
Common Length Conversions
| From | To | Multiply By |
|---|---|---|
| Inches | Centimetres | 2.54 |
| Feet | Metres | 0.3048 |
| Miles | Kilometres | 1.60934 |
| Metres | Feet | 3.28084 |
Common Weight Conversions
| From | To | Multiply By |
|---|---|---|
| Kilograms | Pounds | 2.20462 |
| Pounds | Kilograms | 0.45359237 |
| Stone | Kilograms | 6.35029 |
| Ounces | Grams | 28.3495 |
Temperature Conversion Formulas
Temperature doesn’t convert with a simple multiplier, since the three common scales use different zero points. The formulas are: °F = (°C × 9/5) + 32, °C = (°F − 32) × 5/9, and K = °C + 273.15. Absolute zero, the coldest physically possible temperature, is 0 K, which is −273.15°C or −459.67°F — our calculator won’t let you convert a value below this point.
Frequently Asked Questions
How do I convert between metric, imperial and US customary units?
Select the category that matches what you’re converting (length, weight, volume, area or speed), choose your starting unit and target unit, and enter the value. The calculator applies the correct conversion factor automatically.
Why is temperature conversion different from the other categories?
Length, weight, volume, area and speed each convert using a fixed conversion factor, so you simply multiply by a constant number. Celsius, Fahrenheit and Kelvin use different zero points, so converting between them requires both scaling (multiplying) and an offset (adding or subtracting), rather than a single fixed factor.
How many inches are in a metre?
There are approximately 39.37 inches in a metre. One inch is exactly 2.54 centimetres, so a metre (100 cm) divided by 2.54 gives 39.3701 inches.
What is the difference between a UK gallon and a US gallon?
A UK (imperial) gallon is about 4.546 litres, while a US gallon is about 3.785 litres. A UK gallon is roughly 20% larger than a US gallon, so recipes, fuel economy figures and fluid measurements can differ significantly between the two systems.
How do I convert Celsius to Fahrenheit?
Multiply the Celsius value by 9/5 (or 1.8) and add 32. For example, 20°C × 1.8 = 36, plus 32 gives 68°F.
What is absolute zero?
Absolute zero is the lowest possible temperature, where particles have minimal thermal motion. It is defined as 0 Kelvin, equal to −273.15°C or −459.67°F. No temperature can go below this point.