Unit Converter
Convert length, weight, temperature, volume, area, speed and data — as you type.
Convert between metric and imperial units across seven categories: length (mm to miles), weight (grams to stones), temperature (Celsius, Fahrenheit, Kelvin), volume (ml to gallons), area (m² to acres), speed (km/h, mph, knots) and digital storage (KB to TB). Pick a category, choose your units, and the conversion happens instantly as you type — in both directions.
Precise, not approximate
Mental shortcuts like "double it and add 30" are handy, but this converter uses exact conversion factors (1 inch = 2.54 cm exactly, 1 lb = 453.59237 g) so the result is dependable for recipes, engineering, homework and travel. For the approximations worth knowing by heart, see our metric vs imperial guide.
US vs UK units
Where US and imperial definitions differ — gallons, fluid ounces, cups — the converter labels them separately so you never mix up a 3.79-liter US gallon with a 4.55-liter UK one.
Frequently asked questions
How many kilometers are in a mile?
One mile equals exactly 1.609344 kilometers. A quick mental approximation: multiply miles by 1.6, or remember that 5 miles is roughly 8 km.
How do I convert Celsius to Fahrenheit?
Multiply the Celsius temperature by 9/5 and add 32. For example, 20°C is (20 × 1.8) + 32 = 68°F. A rough mental shortcut is to double the Celsius value and add 30.
What is the difference between a US gallon and a UK gallon?
A US gallon is 3.785 liters while a UK (imperial) gallon is 4.546 liters — about 20% larger. This tool lists them as separate units so conversions are always unambiguous.
Are the conversions exact?
Yes. The converter uses internationally defined conversion factors (for example, 1 inch = 2.54 cm exactly) rather than rounded approximations.