Unit Converter
Convert length, weight, temperature and volume between units.
Convert a value between units in four categories — Length, Weight, Temperature and Volume. Pick a category, choose the From and To units, type a number, and the converted result appears instantly. It covers the everyday metric and imperial units in each group and shows results to four decimal places. Everything is calculated in your browser, so it works offline once loaded and nothing you enter is uploaded.
Four categories and their units
Length offers eight units from millimetres to miles (mm, cm, m, km, inches, feet, yards, miles). Weight has six (mg, g, kg, ounces, pounds, US tons). Temperature covers Celsius, Fahrenheit and Kelvin. Volume has six (millilitres, litres, and US gallons, quarts, cups and fluid ounces). One thing worth flagging: the imperial-style units are the US definitions — a US gallon is 3.78541 litres, which is not the same as a UK gallon — so the menus label them "US" to make that clear.
How the conversion is done
For length, weight and volume the tool converts through a base unit — metres, kilograms and litres respectively. Your value is multiplied by the From unit's factor to reach that base, then divided by the To unit's factor to reach the target. Temperature is handled separately with its own formulas: whatever you enter is converted to Celsius first and then to the target scale (for example Fahrenheit = Celsius x 9/5 + 32, and Kelvin = Celsius + 273.15). Results are shown to a maximum of four decimal places, with thousands separators for large numbers.
Defaults and precision
When you switch category the From box starts on the first unit and To on the second, and the value defaults to 1 so you always see a live example — Length opens on Meters converting to Centimeters, Temperature on Celsius to Fahrenheit. Changing the number or either unit reconverts immediately. Because the output is capped at four decimal places, a very small conversion can round down to 0 or lose a little precision; enter a larger value if you need more significant figures.
Frequently Asked Questions
Which gallon and ounce does the Volume category use?
US customary units. A US gallon is 3.78541 litres and a US fluid ounce is about 29.57 ml, both of which differ from the UK (imperial) versions. The menu labels are marked "US" to make this clear.
How does it convert between units?
For length, weight and volume it uses a base unit (metre, kilogram, litre): it multiplies by the source unit's factor and divides by the target's. Temperature uses dedicated formulas, converting through Celsius.
Why does a very small result show as 0?
Results are rounded to a maximum of four decimal places, so a tiny converted value can display as 0. Use a larger input value to reveal more significant figures.
Does the result update automatically?
Yes. Changing the value or either unit reconverts instantly, and switching category refills both menus. Everything runs in your browser with nothing uploaded.