How to use it
- Pick a category, such as Length or Temperature.
- Type the value and choose the unit you have (From) and the unit you want (To). Use Swap to reverse the direction.
- Read the result, or use the table to see the same value in every unit of the category.
How it works
Conversions use exact definitions wherever they exist. The inch is exactly 2.54 cm and the foot 0.3048 m (the 1959 international yard), so a mile is exactly 1,609.344 m. The pound is exactly 0.45359237 kg, and the ounce is 1/16 of it. The US gallon is defined as 231 cubic inches (3.785411784 L) and the imperial gallon as 4.54609 L, which is why US and imperial measures are listed separately.
Temperature is not a simple ratio: °F = °C × 9/5 + 32 and K = °C + 273.15. Fuel economy is inverse: L/100 km = 235.215 ÷ mpg (US) or 282.481 ÷ mpg (UK). Pressure uses standard gravity (9.80665 m/s²) for psi and the conventional value 133.322387415 Pa for mmHg; energy uses the thermochemical calorie (4.184 J) and the International Table BTU (1,055.05585262 J). Food labels show kilocalories, often written “Calories”.
For digital storage, kB, MB and GB are decimal (1 MB = 1,000,000 bytes) as defined by the SI, while KiB, MiB and GiB are binary (1 MiB = 1,048,576 bytes) as defined by the IEC. Network speeds use bits: 100 Mbit/s moves at most 12.5 MB per second.
Results are shown with up to 10 significant digits, which hides the tiny rounding errors of binary arithmetic. Very large or very small numbers are shown in scientific notation, for example 1.5E-7.
Examples
Height in feet and inches
180 cm ÷ 2.54 = 70.866 in. That is 5 ft (60 in) and 10.87 in, so about 5 ft 11 in. Converting 180 cm to feet directly gives 5.9055 ft.
Oven temperature
A recipe asks for 180 °C. 180 × 9/5 + 32 = 356 °F, so set a Fahrenheit oven to about 350–360 °F.
Car fuel economy
A car using 6.5 L/100 km does 235.215 ÷ 6.5 = 36.2 mpg (US) or 282.481 ÷ 6.5 = 43.5 mpg (UK). The same car, two different mpg numbers.
Frequently asked questions
Why are there two kinds of gallons, pints and fluid ounces?
The US and the UK defined them differently. An imperial gallon (4.546 L) is about 20% larger than a US gallon (3.785 L), and an imperial pint has 20 imperial fluid ounces while a US pint has 16 US fluid ounces.
Is 1 GB 1000 MB or 1024 MB?
By the SI definition 1 GB = 1,000 MB = 1,000,000,000 bytes. The binary unit is the gibibyte: 1 GiB = 1,024 MiB = 1,073,741,824 bytes. Storage makers use GB; many operating systems show GiB values but label them GB.
Why can't I convert 0 L/100 km to mpg?
Zero fuel per distance would mean infinite miles per gallon. Because the units are inverses, the value must be greater than zero.
How precise are the results?
The factors are exact definitions, and results are shown with up to 10 significant digits. That is far more precise than any practical measurement, so round the answer to the precision you need.
What is the difference between weight and mass here?
In everyday use “weight” in kg or lb means mass, and that is what this category converts. Force units such as newtons are not included.
Privacy
All conversions run in your browser. Values you enter are not sent or stored.