Unit Converter
Convert length, weight, temperature and 9 more unit types instantly. Type in either box.
| Unit | Value |
|---|
How to use the unit converter
- Pick a category, such as Length, Weight or Temperature.
- Type a number in either box. The other box updates as you type, in both directions.
- Choose units from the menus, or press ⇄ to swap them.
- Check the table below to see the same value in every unit. Tap a row to make it the target unit.
Converting units, explained simply
Every unit converter works the same way under the hood: each unit is defined as a fixed multiple of one base unit. One inch is exactly 0.0254 meters, one pound is exactly 0.45359237 kilograms and one US gallon is exactly 3.785411784 liters. To convert, the value is turned into the base unit and then into the unit you want. That is why the results here are exact to the last digit shown and do not depend on rounded tables.
Metric and imperial
Most of the world uses the metric system, where units grow in steps of ten: 10 millimeters make a centimeter, 1,000 meters make a kilometer and 1,000 grams make a kilogram. The United States still uses US customary units such as inches, feet, pounds and gallons, and the United Kingdom mixes both, using miles on road signs and pints in pubs. Conversions between the two systems are the most common reason to use a tool like this: a recipe in cups, a TV size in inches or a weight in pounds.
Temperature is different
Celsius, Fahrenheit and Kelvin do not start at the same zero, so you cannot simply multiply. To go from Celsius to Fahrenheit, multiply by 9/5 and add 32, so 20 °C is 68 °F. Kelvin uses the same step size as Celsius but starts at absolute zero, −273.15 °C. Try Celsius to Fahrenheit.
Why a 1 TB drive shows 931 GB
Storage makers use decimal units, where 1 TB is 1,000,000,000,000 bytes. Windows counts in binary units, where one "GB" is really 1,073,741,824 bytes (a gibibyte, GiB). The bytes are all there; they are just counted differently. The Data category shows both kinds side by side. Internet speeds use bits, not bytes: a 100 Mb/s connection downloads at most 12.5 MB per second.
Fuel economy goes both ways
In the US, fuel economy is measured as distance per fuel (miles per gallon), so higher is better. Most other countries use fuel per distance (liters per 100 km), so lower is better. Because one is the inverse of the other, the converter divides instead of multiplying: 30 US mpg is about 7.84 L/100 km. Remember that US and UK gallons are different sizes, so UK mpg figures look about 20% higher for the same car.
Everything runs in your browser. Nothing you type is sent anywhere, and the page keeps working offline once it has loaded.
Frequently asked questions
How many centimeters are in an inch?
Exactly 2.54 centimeters. The inch has been defined as 25.4 millimeters since 1959, so 12 inches (one foot) are 30.48 cm and a 6-foot person is 182.88 cm tall.
How do I convert Celsius to Fahrenheit?
Multiply the Celsius temperature by 9/5 (or 1.8) and add 32. For example, 25 °C × 1.8 + 32 = 77 °F. To go back, subtract 32 and multiply by 5/9. A quick mental estimate is to double the Celsius value and add 30.
Why does my 1 TB drive show only 931 GB?
Drive makers count 1 TB as 10¹² bytes, while Windows divides by 1,024 at each step and still writes "GB". 10¹² ÷ 1,073,741,824 ≈ 931.3, so nothing is missing. macOS uses decimal units and shows the full 1 TB.
What is the difference between a US and a UK gallon?
A US gallon is 3.785 liters and a UK (imperial) gallon is 4.546 liters, about 20% larger. Fluid ounces and pints differ too, so check which one a recipe or a car brochure uses.
How accurate are the results?
The converter uses the official definitions of each unit and shows up to 10 significant digits. Very large or very small numbers are written in scientific notation, such as 1.5 × 10⁻⁹. Months and years use their average length.