Unit Converter
1 inch = 2.54 cm exactly. 1 mile = 1.609344 km exactly. 1 kg = 2.2046 lb (rounded).
How to use
- Choose a category such as Length or Temperature.
- Enter a value and pick the unit to convert from and the unit to convert to. The swap button flips the two.
- The main result is shown at the top, and the same value in every other unit of the category is listed below it.
How it works
Each unit is stored as an exact multiple of one base unit, and a conversion is value × from factor ÷ to factor. The international inch is exactly 0.0254 m and the pound exactly 0.45359237 kg, so a mile is 1.609344 km.
US volumes start from the 231 cubic inch gallon (3.785411784 L). The UK gallon is defined as 4.54609 L, so UK pints and gallons are about 20% larger.
Temperature is converted through kelvin: K = °C + 273.15 and °F = °C × 9 ÷ 5 + 32. Values below absolute zero are rejected.
Data sizes keep the two systems apart. kB, MB, GB and TB step by 1,000 (SI), while KiB, MiB, GiB and TiB step by 1,024 (IEC). A month and a year use the Gregorian average of 365.2425 days.
Quick reference
| Quantity | Exact or derived value |
|---|---|
| 1 inch | 2.54 cm (exact) |
| 1 foot | 0.3048 m (exact) |
| 1 yard | 0.9144 m (exact) |
| 1 mile | 1.609344 km (exact) |
| 1 nautical mile | 1.852 km (exact) |
| 1 pound | 0.45359237 kg (exact) |
| 1 ounce | 28.349523125 g |
| 1 stone (14 lb) | 6.35029318 kg |
| 1 short ton (US, 2,000 lb) | 907.18474 kg |
| 1 long ton (UK, 2,240 lb) | 1,016.0469088 kg |
| 1 US gallon | 3.785411784 L (exact) |
| 1 UK gallon | 4.54609 L (exact) |
| 1 US cup | 236.5882365 mL |
| 1 acre | 4,046.8564224 m² |
| 1 knot | 1.852 km/h (exact) |
Worked examples
- Height of 5 ft 11 in: 5 × 12 + 11 = 71 inches, and 71 × 2.54 = 180.34 cm.
- Body weight of 10 st 7 lb: 10 × 14 + 7 = 147 lb, and 147 × 0.45359237 = 66.678 kg.
- A 350 °F oven: (350 − 32) × 5 ÷ 9 = 176.67 °C.
- A speed of 100 km/h: 100 × 1000 ÷ 1609.344 = 62.14 mph. A speed of 60 mph: 60 × 1.609344 = 96.56 km/h.
- A 1 TB drive: 10¹² ÷ 2⁴⁰ = 0.9095 TiB, which is 931.32 GiB.
- A 100 Mbit/s connection: 100 ÷ 8 = 12.5 MB/s at best.
Temperature reference
| °C | °F | Note |
|---|---|---|
| −40 | −40 | The scales meet here |
| 0 | 32 | Water freezes |
| 20 | 68 | Typical room temperature |
| 37 | 98.6 | Typical body temperature |
| 100 | 212 | Water boils at sea level |
| 180 | 356 | Common baking temperature |
| 220 | 428 | Hot oven |
Places conversions go wrong
- A ton is three different weights: 907 kg for the US short ton, 1,016 kg for the UK long ton and exactly 1,000 kg for the metric tonne.
- A pint is 473 mL in the US and 568 mL in the UK. A US cup (237 mL) is not the metric cup used in some countries.
- A temperature difference converts differently from a reading. A rise of 10 K or 10 °C is a rise of 18 °F, because the 32 offset does not apply to differences.
- Decimal and binary data units are different. 1 GB is 10⁹ bytes and 1 GiB is 2³⁰ bytes, about 7% larger.
FAQ
Why does my 1 TB drive show as 931 GB?
Drive makers use decimal terabytes (10¹² bytes), while some operating systems count in binary units and label them GB. 1 TB equals 931.32 GiB.
Are US and UK cups and pints the same?
No. A US pint is 473.18 mL and a UK pint is 568.26 mL. Choose the matching unit when following a recipe.
How many decimal places are shown?
Results are rounded to 12 significant digits to hide floating-point noise, then shown with up to 8 decimal places.
How do I convert feet and inches to centimetres?
Convert everything to inches (feet × 12 + inches), then multiply by 2.54. 5 ft 11 in is 71 in, which is 180.34 cm.
What is the difference between a ton and a tonne?
A tonne is the metric unit, exactly 1,000 kg. A ton in the US is 2,000 lb (907.18 kg), and in the UK it is 2,240 lb (1,016.05 kg).
Why does a UK gallon give a different number of litres?
The UK gallon is defined as 4.54609 L, while the US gallon is 3.785411784 L. A UK gallon is about 20% larger.