Unit conversions you can check.
Exact factors from NIST and the SI, the formula and a worked example on every page, inch fractions for the tape measure and cups to grams by ingredient.
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Browse by category
- LengthMillimeters, centimeters, inches, feet, meters and miles, with inch fractions.
- WeightGrams, kilograms, ounces, pounds, stones and tons.
- TemperatureCelsius, Fahrenheit and kelvin, with an oven temperature chart.
- VolumeLiters, gallons, quarts, pints and cubic units, US and imperial.
- AreaSquare feet, square meters, acres and square miles.
- CookingCups, spoons and milliliters, and cups to grams by ingredient.
- SpeedKilometers per hour, miles per hour, knots and meters per second.
- Energy and powerJoules, calories, watts, kilowatts, torque and voltage.
- Data sizeKilobytes, megabytes and gigabytes, decimal and binary, and pixels to inches.
- TimeHours, minutes and seconds, decimal hours, time clock and 24-hour time.
Most used conversions
All conversions- Centimeters to Inches1 cm ≈ 0.393701 in.
- Inches to Centimeters1 in = 2.54 cm.
- Millimeters to Inches1 mm ≈ 0.0393701 in.
- Kilograms to Pounds1 kg ≈ 2.20462 lb.
- Pounds to Kilograms1 lb = 0.45359237 kg.
- Celsius to Fahrenheit20 °C = 68 °F. °F = (°C × 9/5) + 32.
- Cups to GramsBy ingredient: 1 cup of flour is 120 g, sugar 198 g, butter 226 g.
- Height ConverterFeet and inches to centimeters and back. 5 ft 7 in = 170.18 cm.
Charts you can print
- Inch fractions to millimetersEvery 1/64 of an inch as a decimal and in mm. All values exact.
- Kitchen measuresCups, tablespoons, teaspoons, fluid ounces and milliliters, plus one cup in grams by ingredient.
- Oven temperaturesCelsius to Fahrenheit and back for every common oven setting.
- Height in cm to feet and inchesEvery centimeter from 140 to 210.
Why the numbers here are right
Each unit is defined once, as an exact value: 1 inch is 0.0254 m, 1 pound is 0.45359237 kg, 1 US gallon is 231 cubic inches. Every converter and chart on the site is generated from that one list, the arithmetic is done on exact fractions, and a result is rounded once, to the precision you pick. How we calculate has the details and the sources.