Convert length, weight, volume, speed, temperature and sizes between metric and imperial in one click.
Our unit converters turn everyday measurements into the unit you need. Switch centimeters to feet, kilograms to pounds, kilometers to miles, liters to gallons or Celsius to Fahrenheit, and convert cooking amounts, speeds and clothing sizes without searching for a formula.
How do I convert metric units to imperial?
To convert metric to imperial, multiply by the correct conversion factor: for example, 1 kilometer equals 0.6214 miles and 1 kilogram equals 2.2046 pounds. Our unit converters apply these factors automatically, show the formula and let you reverse the direction with one click.
Europe uses metric units, while the UK mixes metric and imperial in road signs, pints and body weight, and many online recipes, products and sports use US units. These converters bridge that gap with precise results and the formula shown beside each answer, plus regional tools for land and gold units.
Length and Speed
Centimeters, inches, feet, meters, miles and speed
Weight, Volume and Cooking
Kilograms, grams, ounces, liters, cups and more
Temperature and Sizes
Celsius, Fahrenheit, shoe and clothing sizes
Regional Units
Land area and gold weight units used in South Asia
Kitchen, Area and Power Conversions
Cups, spoons, ounces, square feet, watts and body weight
More Converters
Popular conversions, weather, tires and recipes
Why Do Unit Converters Give Slightly Different Answers?
Unit converters disagree only when one of them rounds the conversion factor, because the main factors are exact by definition: 1 inch is exactly 2.54 cm and 1 pound is exactly 0.45359237 kg. These values come from the 1959 international yard and pound agreement and are listed in NIST Special Publication 811.
Rounding errors grow with the size of the number. Using 0.45 instead of 0.45359237 to convert 90 kg gives 200 pounds rather than 198.4, a gap that matters for luggage limits or medication doses. A reliable converter uses the full factor and rounds only the final answer.
The NIST quick reference card for approximate conversions still uses short factors such as 2.54 for inches and 3.79 for gallons, which are fine for estimates. For anything you will order, cut or weigh, use an exact tool such as the kg to lbs converter or the cm to feet converter.
Europe uses metric units for almost everything, but imperial measures survive in everyday British life: road signs show miles, beer is sold in pints and many people still give their height in feet and inches. That mix is why quick, accurate conversion is useful even for people who never leave the UK.
Are UK and US Gallons the Same Size?
No: an imperial (UK) gallon is exactly 4.54609 liters, while a US gallon is 3.785411784 liters, so the UK gallon is about 20 percent larger. This difference catches out drivers comparing fuel economy, because a car rated in miles per UK gallon looks more efficient than the same car rated in miles per US gallon.
Smaller units differ too. A UK pint is about 568 ml and a US pint about 473 ml, and a UK fluid ounce is about 28.41 ml against 29.57 ml for a US fluid ounce. Recipes from American websites therefore need converting with the US figures, not the UK ones.
The liters to gallons converter lets you choose which gallon you mean. Fuel in the UK and Ireland is sold by the liter, so the liter figure is usually the one to start from.
Even within one country, labels can mix systems. Older UK recipes list fluid ounces and pints, while modern packaging uses milliliters, so a converter that names which system it uses saves guesswork in the kitchen.
How Do You Convert Celsius to Fahrenheit Without a Calculator?
The exact rule is °F = °C × 1.8 + 32, and a quick mental shortcut is to double the Celsius figure and add 30. The shortcut gives 70 for 20 °C, close to the exact 68 °F, but it drifts further from the truth at very high or low temperatures.
A few anchor points help: 0 °C is 32 °F, 37 °C is 98.6 °F, 100 °C is 212 °F and minus 40 is the same on both scales. To go the other way, subtract 32 and divide by 1.8, which is the formula NIST gives for converting Fahrenheit to Celsius.
Oven settings are a good test. A recipe set at 180 °C needs 356 °F, which most ovens round to 350 °F, while 200 °C is 392 °F, usually set as 400 °F. Fan ovens often run hotter, so many recipes suggest lowering the temperature by about 20 °C when using one.
For weather, the shortcut is usually close enough, but for cooking, medicine or science it is better to use an exact tool such as the Celsius to Fahrenheit converter, which applies the full formula and avoids rounding surprises.
| From | To | Factor | Status |
|---|---|---|---|
| 1 inch | centimeters | 2.54 | Exact by definition |
| 1 foot | meters | 0.3048 | Exact by definition |
| 1 mile | kilometers | 1.609344 | Exact by definition |
| 1 pound | kilograms | 0.45359237 | Exact by definition |
| 1 US gallon | liters | 3.785411784 | Exact by definition |
| 1 UK gallon | liters | 4.54609 | Exact by definition |
| Degrees Celsius | degrees Fahrenheit | × 1.8, then + 32 | Exact formula |
Frequently Asked Questions
How accurate are the unit converters?
They use exact or internationally agreed conversion factors, such as 2.54 centimeters per inch, and show results to a sensible number of decimal places. You can change the precision if you need more or fewer digits.
Which countries use the metric system?
Almost every country uses metric, including all EU states. The United States, Liberia and Myanmar are the main exceptions, and the UK uses a mix, with metric for most trade but miles, pints and stones in daily life.
Can I convert in both directions?
Yes. Every converter has a swap button, so you can go from centimeters to feet and then back to centimeters without opening another page. The formula shown updates to match the direction you choose.
Are US and UK gallons and ounces the same?
No. A US gallon is about 3.785 liters while a UK imperial gallon is about 4.546 liters, and fluid ounces differ slightly too. Our converters label which version they use so recipes and fuel figures stay correct.
Are shoe and clothing size conversions exact?
No. Sizes vary by brand and country, so conversions are close guides, not exact matches. Use them to narrow your choice, then check the retailer size chart and reviews before ordering, especially for shoes.
Sources and Further Reading
- NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically
- NIST: Approximate Conversions from U.S. Customary Measures to Metric
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Last reviewed: October 2026