Metric vs Imperial: A Plain-English Guide to Both Systems
Why the world uses two measurement systems, how they differ, and the handful of conversion anchors that make switching between them easy.
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Milliliters to Fluid Ounces1 ml = 0.033814 fl ozInches to Centimeters1 in = 2.54 cmGallons to Liters1 gal = 3.78541 LCups to Pints1 cup = 0.5 ptMiles to Kilometers1 mi = 1.60934 kmPounds to Kilograms1 lb = 0.453592 kgCelsius to Fahrenheit20 °C = 68 °FSquare Feet to Square Meters1 ft² = 0.092903 m²Calories to Kilojoules1 kcal = 4.184 kJMiles per Hour to Kilometers per Hour1 mph = 1.60934 km/hCentimeters to Inches1 cm = 0.393701 inKilometers to Miles1 km = 0.621371 miKilograms to Pounds1 kg = 2.20462 lbLiters to Gallons1 L = 0.264172 galCups to Milliliters1 cup = 236.588 mlFahrenheit to Celsius68 °F = 20 °CSquare Meters to Square Feet1 m² = 10.7639 ft²Kilojoules to Calories1 kJ = 0.239006 kcalMegabits per Second to Megabytes per Second1 Mbps = 0.125 MB/sKilometers per Hour to Miles per Hour1 km/h = 0.621371 mphBars to Pounds per Square Inch1 bar = 14.5038 psiKilowatts to Horsepower1 kW = 1.34102 hpUS to UK Shoe Sizes
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Exact, not approximate
We use the official definitions of every unit, so an inch is exactly 25.4 mm and a pound is exactly 0.45359237 kg. No rounded shortcuts behind the scenes.
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Each page explains the formula, gives worked examples and a reference table, and covers the pitfalls such as US versus imperial gallons.
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From the guides
All guides →Cooking Measurement Conversions: A Cheat Sheet for Cups, Spoons and Grams
Convert cups, tablespoons, teaspoons, milliliters, grams and oven temperatures with confidence, whichever country your recipe comes from.
Read guideCelsius vs Fahrenheit: How to Convert Temperatures in Your Head
A quick history of the two scales, the exact formulas, and simple mental tricks to estimate temperatures without a calculator.
Read guideFrequently asked questions
Are the converters accurate?
Yes. Each converter uses the internationally defined value of every unit, such as exactly 25.4 mm per inch and exactly 0.45359237 kg per pound. Every page shows the formula and the factor so you can verify the result.
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Do you store the numbers I enter?
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Can I convert between any two units?
On every converter page you can choose any unit in that category from the From and To drop-downs, or use the swap button to reverse the direction.