Unit converter
Pick what you are measuring, type a number and choose the units. Every other unit is listed underneath.
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In every unit
Common conversions
These are the answers the converter gives, rounded to 7 significant digits.
| From | To | From | To |
|---|---|---|---|
| 1 inch | 2.54 cm | 1 kilogram | 2.204623 lb |
| 6 feet | 1.8288 m | 1 pound | 453.5924 g |
| 1 mile | 1.609344 km | 10 stones | 63.50293 kg |
| 10 km | 6.213712 miles | 1 US cup | 236.5882 ml |
| 60 mph | 96.56064 km/h | 1 US gallon | 3.785412 liters |
| 100 km/h | 62.13712 mph | 1 UK gallon | 4.54609 liters |
| 20 °C | 68 °F | 1 acre | 4,046.856 m² |
| 98.6 °F | 37 °C | 1,000 square feet | 92.90304 m² |
A 350 °F oven is 176.6667 °C, which recipes round to 175 or 180 °C. A 10 km race is 6.21 miles, and 1,000 square feet is a little under 93 square meters, the size of a mid-sized apartment.
US and UK units are not the same
Gallons, pints and fluid ounces have the same names in the United States and the United Kingdom but different sizes, which is why a pint of beer in London is bigger than one in New York. The list keeps them apart: pick "US gallons" or "UK gallons". The UK fluid ounce is the odd one out, a little smaller than the US one, because a UK pint holds 20 fluid ounces and a US pint 16.
| Unit | United States | United Kingdom | Difference |
|---|---|---|---|
| Fluid ounce | 29.57353 ml | 28.41306 ml | UK is 4% smaller |
| Pint | 473.1765 ml | 568.2613 ml | UK is 20% bigger |
| Gallon | 3.785412 liters | 4.54609 liters | UK is 20% bigger |
| Ton | 907.1847 kg (2,000 lb) | 1,016.047 kg (2,240 lb) | UK is 12% bigger |
A metric ton, often spelled tonne, is 1,000 kg, between the two.
Length and weight units are shared. Since the 1959 international agreement (NIST lists the exact factors in Special Publication 811), an inch is exactly 2.54 cm and a pound exactly 0.45359237 kg in both countries, and every other unit here follows from those numbers, so the converter's factors are exact rather than measured. The UK gallon is fixed at exactly 4.54609 liters in the Weights and Measures Act 1985.
How the conversion works
Each unit is stored as an exact multiple of one base unit (meters, kilograms, liters, square meters, meters per second or seconds). To convert, the value is multiplied by the first unit's factor and divided by the second's: 60 mph is 60 × 1,609.344 ÷ 3,600 meters per second, then divided by 1,000 ÷ 3,600 to give km/h. Temperature can't work that way because the scales start at different zeros, so it goes through Celsius: °F = °C × 9/5 + 32, and kelvin = °C + 273.15.
Questions
How many centimeters are in an inch?
Exactly 2.54. The inch has been defined as 2.54 cm since 1959, so the conversion never changes.
How do I convert centimeters to inches?
Divide by 2.54. 30 cm is 30 ÷ 2.54 = 11.81 inches. Pick Length, set From to centimeters and To to inches, and type the number above.
What is the difference between an inch and a centimeter?
An inch is the US customary unit and a centimeter is the metric one; one inch is about two and a half centimeters. Rulers often show both, with inches on one edge and centimeters on the other.
How many millimeters are in a centimeter?
Ten. Metric units go up in steps of ten, a hundred or a thousand: 10 mm in a centimeter, 100 cm in a meter, 1,000 m in a kilometer.
Why does the answer have so many decimals?
Results are shown to 7 significant digits so nothing important is lost. Round to what you need: for a recipe, 236.5882 ml is simply 240 ml; for engineering, keep the digits.
Can I convert a negative temperature?
Yes, down to absolute zero: −273.15 °C, −459.67 °F or 0 K. A colder number than that can't exist, so the converter says so instead of giving an answer.
How long is a year here?
365.25 days, which counts a leap year every four years. This is the year astronomers use. The calendar on your wall skips three leap years every 400 years, so its average year is 365.2425 days, a difference of about 11 minutes a year. For counting the real days between two dates, use days between dates.