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Unit Converters

Exact unit conversions for length, volume, weight, temperature, area, angle and speed — metric and US customary. Type a value, pick two units, and swap them with one tap.

Each converter covers one kind of measurement and lists both metric and US customary units. Pick a unit to convert from and one to convert to, type a value, and the converted value updates as you type; the swap button reverses the direction, and the result lists the exact definition of each unit.

How to choose the right calculator

Distance, height and size

For inches, feet, miles or meters, use the length converter. For the size of a floor, a lot or a field, use the area converter; to measure a room from its dimensions instead, the square footage calculator does the multiplication for you.

Cooking, liquids and weight

For recipes and liquids, such as cups, tablespoons, milliliters or gallons, use the volume converter. For body weight, groceries or shipping, such as pounds, ounces, kilograms or stone, use the weight converter.

Weather, travel and geometry

For Fahrenheit, Celsius and kelvin, use the temperature converter. For mph, km/h or knots, use the speed converter. For degrees, radians and other angle units, use the angle converter.

Guide to each converter

Length Converter

Converts between millimeters, centimeters, meters, kilometers, inches, feet, yards, miles and nautical miles. Open the length converter.

Volume Converter

Converts between milliliters, liters, cubic meters, US teaspoons, tablespoons, fluid ounces, cups, pints, quarts and gallons, and UK imperial gallons. Open the volume converter.

Weight Converter

Converts between milligrams, grams, kilograms, metric tonnes, ounces, pounds and stone. Open the weight converter.

Temperature Converter

Converts between Celsius, Fahrenheit and kelvin, and flags values below absolute zero. Open the temperature converter.

Area Converter

Converts between square centimeters, square meters, hectares, square kilometers, square inches, square feet, square yards, acres and square miles. Open the area converter.

Angle Converter

Converts between degrees, arcminutes, arcseconds, radians, gradians and turns. Open the angle converter.

Speed Converter

Converts between kilometers per hour, meters per second, miles per hour and knots. Open the speed converter.

US customary, imperial and metric

Several unit names mean different amounts depending on the system. A US gallon and a UK imperial gallon are different sizes, so the volume converter lists them separately, and the cooking measures are labeled as US cups, tablespoons and teaspoons. When a recipe or a spec sheet comes from another country, check which system it uses before converting, and pick the matching unit from the list.

Exact factors and rounding

Rules of thumb like 'a meter is about three feet' are fine for a rough idea but add up quickly in a project. The converters use exact definitions and keep full precision while converting, then round only the number on screen. If you need a factor for a spreadsheet or a formula, the result shows the exact definition of each unit and, for every converter except temperature, the reverse factor for converting back.

About our unit converters

Every converter here uses the exact legal definitions of each unit, the same ones published by NIST: an inch is exactly 2.54 centimeters, a pound exactly 0.45359237 kilograms, and a US gallon exactly 231 cubic inches. Values are carried at full precision and only rounded for display, so converting back and forth gives you the number you started with. Temperature is handled as an offset scale, not a simple factor, and cooking measures are clearly labeled as US customary so you never mix up a US cup with a metric or imperial one.