How to use it
- 1Pick a category, such as length, temperature or data size.
- 2Type a value and choose the units to convert from and to. Decimals work with a comma or a point.
- 3The result updates as you type. Use the swap button to convert in the other direction.
- 4See the table below for the value in every unit of the category. The address bar always holds a link to the current conversion, ready to share.
Exact definitions behind the numbers
Since 1959 the yard and the pound have been defined in metric units: an inch is exactly 25.4 mm, a foot 0.3048 m, a mile 1,609.344 m and a pound 0.45359237 kg. The converter uses these exact definitions and shows results with up to 12 significant digits, switching to scientific notation for very large or very small values.
US and British units with the same name aren’t always equal. A US gallon is 3.785411784 litres and an imperial gallon 4.54609 litres, so a British pint (568 ml) is about 20 % larger than an American one (473 ml). Both are listed and labelled separately.
GB or GiB? Why a 1 TB drive shows 931 GB
Drive makers count in decimal units, where 1 GB is 1,000,000,000 bytes. Windows and many other programs count in binary units, where 1 GiB is 1,073,741,824 bytes (2³⁰) – and often still call them GB. A 1 TB drive therefore appears as about 931 GB, although no space is missing.
Internet speeds are given in bits per second, while downloads show bytes. There are 8 bits in a byte, so a 100 Mbit/s connection downloads at most 12.5 MB/s, or about 11.9 MiB/s.
Temperature and fuel economy
Celsius and Fahrenheit start from different zero points, so converting them takes more than one multiplication: °F = °C × 9/5 + 32, which makes 20 °C equal to 68 °F. Kelvin starts at absolute zero, −273.15 °C, and uses degrees the size of Celsius ones; Rankine does the same for Fahrenheit.
Litres per 100 km measure how much fuel a car uses over a distance, while miles per gallon measure how far it goes on a set amount of fuel. One is the reciprocal of the other: a lower L/100 km figure is better, a higher mpg figure is better. 5 L/100 km is about 47 US mpg or 56.5 UK mpg.
Questions and answers
How many kilometres are in a mile?
One mile is exactly 1.609344 kilometres, and one kilometre is about 0.621 miles. For a quick estimate, multiply miles by 1.6 or kilometres by 0.6 – a 5 km run is about 3.1 miles.
How do I convert Celsius to Fahrenheit?
Multiply by 1.8 and add 32: 25 °C × 1.8 + 32 = 77 °F. For the other direction, subtract 32 and divide by 1.8. At −40 both scales show the same number.
How many pounds are in a kilogram?
One kilogram is about 2.20462 pounds, and one pound is exactly 0.45359237 kg. A quick estimate: double the kilograms and add 10 % – 70 kg is about 154 lb.
Why is my 1 TB hard drive only 931 GB?
The drive holds 1,000,000,000,000 bytes, as advertised. Your computer divides that by 1,073,741,824 (a binary gigabyte, properly called a GiB) instead of 1,000,000,000, which gives about 931. Choose Data size and convert TB to GiB to see the exact figure.
How do I convert L/100 km to mpg?
Divide 235.215 by the consumption in litres per 100 km to get US miles per gallon, or 282.481 for UK (imperial) miles per gallon. The same numbers work the other way: 235.215 ÷ 30 US mpg ≈ 7.84 L/100 km.