Unit converter
Pick a category, type a number, and see it in every unit of that category at once, or compare two units with a swap button. Answers are exact: no rounding noise, and you choose how many digits to show. It handles US, imperial and metric units, decimal and binary data sizes, and fuel economy in both directions. Nothing is sent anywhere.
Category
Feet, yards and miles here are the international ones. The older US survey foot, retired at the end of 2022, differs by about 2 parts per million and is not used.
Use a decimal point or a decimal comma. Scientific notation works (1.5e3). Do not type thousands separators.
Result
Read as 1 mi
≈ 1.60934 km
Mile → Kilometer
Common conversions
1 mi in every unit
| Unit | Symbol | Value |
|---|---|---|
| Metric | ||
| Kilometer | km | ≈ 1.60934 |
| Meter | m | ≈ 1609.34 |
| Centimeter | cm | ≈ 160934 |
| Millimeter | mm | ≈ 1609340 |
| Micrometer | µm | ≈ 1609340000 |
| Nanometer | nm | ≈ 1609340000000 |
| US customary | ||
| Inch | in | 63360 |
| Foot | ft | 5280 |
| Yard | yd | 1760 |
| Mile | mi | 1 |
| Other | ||
| Nautical mile | nmi | ≈ 0.868976 |
Values marked with ≈ are rounded to 6 significant digits. Pick "Exact" to see every digit.
How units are defined
Every factor below is exact, not rounded. This page stores them as fractions of whole numbers, so nothing is ever converted through a floating-point number.
| Unit | Exactly equal to (m) |
|---|---|
| 1 km (Kilometer) | = 1000 m |
| 1 m (Meter) | = 1 m |
| 1 cm (Centimeter) | = 0.01 m |
| 1 mm (Millimeter) | = 0.001 m |
| 1 µm (Micrometer) | = 0.000001 m |
| 1 nm (Nanometer) | = 1e-9 m |
| 1 in (Inch) | = 0.0254 m |
| 1 ft (Foot) | = 0.3048 m |
| 1 yd (Yard) | = 0.9144 m |
| 1 mi (Mile) | = 1609.344 m |
| 1 nmi (Nautical mile) | = 1852 m |
Where the definitions come from
- •Since the international yard and pound agreement of 1959: 1 inch = 25.4 mm exactly, 1 foot = 0.3048 m, 1 yard = 0.9144 m, 1 mile = 1609.344 m, 1 pound = 0.45359237 kg.
- •1 US gallon = 231 cubic inches = 3.785411784 L. The US quart, pint, cup, fluid ounce, tablespoon and teaspoon are 1/4, 1/8, 1/16, 1/128, 1/256 and 1/768 of a US gallon, so a US cup is 236.5882365 mL.
- •1 imperial gallon = 4.54609 L. The imperial quart, pint and fluid ounce are 1/4, 1/8 and 1/160 of it.
- •1 nautical mile = 1852 m exactly. 1 knot = 1 nautical mile per hour.
- •1 thermochemical calorie = 4.184 J, so 1 kcal = 4184 J. 1 kWh = 3.6 million J. 1 BTU (International Table) = 1055.05585262 J. 1 eV = 1.602176634e-19 J (fixed in the 2019 SI).
- •1 standard atmosphere = 101325 Pa. 1 mmHg = 133.322387415 Pa (conventional mercury density times standard gravity). 1 psi = 1 pound-force per square inch, where 1 pound-force = 4.4482216152605 N.
- •1 mechanical horsepower = 550 foot-pounds-force per second = 745.69987158227022 W. 1 metric horsepower (PS) = 735.49875 W.
- •Data: 1 byte = 8 bits. Kilo-, mega-, giga- are powers of 1000; kibi-, mebi-, gibi- are powers of 1024.
- •Metric cooking spoons and cups (5 mL, 15 mL, 250 mL) are the common metric kitchen sizes; the Australian tablespoon is 20 mL.
Why there is no currency
A meter is always the same length, but a dollar is worth a different number of euros every minute. Currency needs live rates from a data feed, and this page works offline with no network requests, so it does not include currency rather than show you an out-of-date rate.
How it works
- •Every unit is stored as an exact fraction of its category's base unit (for example 1 inch = 25.4 mm exactly), using whole-number arithmetic rather than floating-point numbers. That is why 0.1 and 0.2 never turn into 0.30000000000000004.
- •You choose how many significant digits to show: 4, 6, 10 or exact. Rounded values carry an ≈ sign. Exact shows every digit when the decimal ends, and the exact fraction when it never does.
- •Temperature uses formulas (Celsius, Fahrenheit, Kelvin, Rankine) and refuses anything below absolute zero. Fuel economy treats miles per gallon and liters per 100 km as inverses, so 30 mpg (US) is 7.84049 L/100 km.
- •Type a decimal point or a decimal comma, and scientific notation such as 1.5e3 works. Thousands separators are rejected on purpose, because 1,234 could mean 1234 or 1.234 and the page will not guess.
- •Cooking is limited to volume to volume (cups, tablespoons, teaspoons, mL). Cups to grams depends on the ingredient, so it is not offered. Currency is not included either, because rates change every minute.
Questions
- How exact are the conversions?
- Exact to the definitions listed on the page, which come from the international yard and pound agreement of 1959, NIST and the SI. An inch is exactly 25.4 mm, a pound exactly 0.45359237 kg, a US gallon exactly 3.785411784 L. The only approximate unit is the radian, because pi never ends; it is marked.
- Why is a 1 TB drive about 931 GB on my computer?
- Makers count in powers of 1000 (1 TB = 1,000,000,000,000 bytes). Some operating systems divide by powers of 1024 and still write "GB", but the unit is really GiB: 1 TB is 931.3225746 GiB. This page shows KB, MB, GB (decimal) and KiB, MiB, GiB (binary) in separate groups so you can see both.
- Can it convert cups to grams?
- No. Cups measure volume and grams measure mass, and how much a cup weighs depends on what is in it: flour, sugar and honey are all different. It can convert a US cup (236.5882365 mL) to a metric cup (250 mL), tablespoons and teaspoons, which are all volume to volume.
- Is 30 mpg the same in the US and the UK?
- No. The imperial gallon (4.54609 L) is bigger than the US gallon (3.785411784 L), so 30 mpg (imperial) is 24.9802 mpg (US) and the other way round. The page keeps both and also shows liters per 100 km, which is the same everywhere.