📏 Unit Converter

Convert between all units instantly — length, weight, temperature, volume, speed, area and more.

What this converter covers

The converter handles 81 units in ten categories: length (10 units), weight (8), temperature (4), volume (11), speed (6), area (8), time (9), data (9), pressure (8) and energy (8). Pick a category, choose the unit to convert from and to, and type a value. The answer updates as you type, and a table beside it shows the same pair for common values: 1, 5, 10, 50, 100, 500 and 1,000. The sums run in your browser and nothing you type is sent anywhere.

How the conversions work

Every unit is stored as a factor relative to one base unit per category (metre, kilogram, litre, square metre, second, byte, pascal, joule and kilometre per hour). To convert, the value is multiplied by the "from" factor and divided by the "to" factor. Temperature is the exception: Celsius, Fahrenheit, Kelvin and Rankine have different zero points, so each value goes through Celsius using its own formula, such as °F = °C × 9 ÷ 5 + 32.

Worked examples

Length. 5 miles = 5 × 1,609.344 m = 8.04672 km. 6 feet = 72 inches.
Weight. 70 kg ÷ 0.453592 = 154.32 lb. One stone is 6.35029 kg.
Temperature. 100 °F = (100 − 32) × 5 ÷ 9 = 37.78 °C. A 350 °F oven is 176.67 °C. −40 is the same on both scales.
Speed. 100 km/h = 62.14 mph.
Area. 1 acre = 4,046.86 m² = 0.4047 hectares.
Energy. 1 kWh = 3,600,000 J. A 2,000-kcal day is 8,368 kJ.

Things that trip people up

US and UK gallons differ. A US gallon is 3.78541 litres and a UK gallon is 4.54609 litres, so 1 UK gallon is about 1.2 US gallons. Cups, pints, quarts, fluid ounces, tablespoons and teaspoons in this converter are US measures. Cooking cups differ by country, so check the recipe's origin.
Data units use 1,024, not 1,000. Here 1 KB = 1,024 bytes, 1 MB = 1,048,576 bytes and 1 GB = 1,024 MB. Strictly those are kibibytes, mebibytes and gibibytes. Drive makers and many network and phone plans use 1 GB = 1,000,000,000 bytes, which is why a "500 GB" drive shows as about 465 GB in some operating systems. Bits are a different unit from bytes: 8 bits make 1 byte, and internet speeds are usually quoted in bits.
Calories. The "calorie" (cal) here is the small thermochemical calorie, 4.184 J, and one kilocalorie is 1,000 of them. The "Calories" on food labels are kilocalories.
Months and years in the time category are averages. A month is 30.44 days and a year is 365.2425 days. For exact calendar spans use the date calculator.
Mach is not a fixed speed. It depends on air temperature and altitude. The value used here, 1,234.8 km/h, corresponds to 343 m/s, the speed of sound in dry air at 20 °C.
Very large and very small answers. Results of 1,000,000 or more, or below 0.0001, appear in scientific notation, for example 8.368e+6 for 8,368,000. The value is the same, just written in a shorter form.

For money rather than measurements, use the currency converter.

Frequently Asked Questions

All conversions use precise standard conversion factors (for example, 1 mile = 1609.344 meters exactly) and display results with appropriate decimal precision, switching to scientific notation for very large or very small numbers so nothing gets rounded away.

Length, weight, and most other categories convert by multiplying by a fixed factor. Temperature scales don't share a common zero point, so Celsius, Fahrenheit, Kelvin, and Rankine each need their own formula (for example, °F = °C × 9/5 + 32) rather than a simple multiplier.

The US primarily uses the imperial system (miles, pounds, Fahrenheit) while most other countries use metric (kilometers, kilograms, Celsius) — a historical holdover rather than a technical advantage. This is exactly why a converter is useful: recipes, product specs, and travel distances often need translating between the two systems.