Conversions calculators
Since 1959 the inch, foot, yard, mile, and pound have each been defined as an exact multiple of the metre or the kilogram. These converters use those exact definitions, so a result is as precise as the number of decimal places you ask for, not a rounded rule of thumb.
Most converters show every related unit at once, which makes it easy to check the answer against a unit you already have a feel for.
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- Celsius to Fahrenheit ConverterTurn Celsius into Fahrenheit, or Fahrenheit into Celsius, with each step shown, a quick mental shortcut and a handy chart.
- Centimeters to Inches ConverterTurn centimeters into inches, or inches into centimeters, with tape-measure fractions, feet and inches, and a handy chart.
- Height ConverterChange a height in feet and inches into centimeters and meters, or back again. Includes a handy height chart.
- Kilograms to Pounds ConverterChange kilograms to pounds (or pounds and ounces), or pounds to kilograms, using the exact number. See the working and a full chart.
- Watts to Amps ConverterConvert watts to amps, amps to watts, or find the voltage, for DC, single-phase AC and three-phase AC, with a chart of common wattages.
- Cups to Fluid Ounces ConverterConvert US cups to US fluid ounces or fluid ounces to cups, and learn when an ounce means weight instead of volume.
- Feet to Meters ConverterConvert feet to meters or meters to feet with the exact 0.3048 factor, step-by-step working and a quick-reference table.
- Inches to Feet ConverterChange inches to feet or feet to inches (12 inches per foot), with the steps shown and a table of common heights and lengths.
- Kilometers to Miles ConverterTurn kilometers into miles, or miles into kilometers, using the exact 1.609344 factor, with common race distances in a handy table.
- Length ConverterChange any length from one unit to another, from millimeters to miles, inches to kilometers, and nautical miles, using exact definitions.
- Milliliters to Fluid Ounces ConverterConvert milliliters to US fluid ounces or fluid ounces to milliliters, with the exact factor and a table of bottle and can sizes.
- MPH to km/h ConverterConvert miles per hour to kilometers per hour or km/h to mph with the exact mile, for road speeds, running and cycling.
- Ring Size ConverterTurn a finger or ring measurement in mm, cm or inches into approximate US, UK, EU and Japanese ring sizes, or convert between those sizes.
- Shoe Size ConverterConvert adult shoe sizes between US men's, US women's, UK, EU and Japanese sizes, or find approximate sizes from a foot length.
- Temperature ConverterChange a temperature between Celsius, Fahrenheit, Kelvin and Rankine, with each step of the math shown and no readings below absolute zero.
- Weight ConverterConvert between pounds, kilograms, ounces, grams, stones and tons using the exact international definitions.
- Acres to Hectares ConverterTurn acres into hectares, or hectares into acres, using the exact factor. You also get the working and a table of common land sizes.
- Acres to Square Feet ConverterConvert acres to square feet or square feet to acres for lot sizes, using the exact 43,560 square feet per acre.
- Angle ConverterConvert angles between degrees, radians, gradians, turns, arcminutes and arcseconds. Or switch between degrees-minutes-seconds and decimal degrees.
- Area ConverterConvert areas between square millimeters, square meters, hectares, square feet, acres, square miles and more using exact factors.
- Bra Size CalculatorEstimate a starting bra size from underbust and bust measurements, with US, UK, EU and Australian equivalents and sister sizes.
- Celsius to Kelvin ConverterTurn a Celsius temperature into kelvins, or kelvins back into Celsius, by adding or subtracting 273.15. It checks for absolute zero and includes a lab reference table.
- Centimeters to Feet ConverterConvert centimeters to feet or feet to centimeters with the exact 30.48 factor, plus how to split decimal feet into feet and inches.
- Cubic Feet to Cubic Meters ConverterConvert cubic feet to cubic meters or cubic meters to cubic feet with the exact factor, for shipping, storage, appliances and gas.
- Cubic Feet to Gallons ConverterConvert cubic feet to US gallons or gallons to cubic feet using the exact 1728/231 ratio, for pools, tanks, aquariums and water.
- Cups to Milliliters ConverterConvert US cups to milliliters or milliliters to cups for recipes, with the exact cup size and the metric-cup difference explained.
- Density ConverterChange a density from one unit to another using exact factors. Choose from kg/m³, g/cm³, g/mL, lb/ft³, lb/gal, oz/in³, slugs per cubic foot and more.
- Energy ConverterChange an amount of energy from one unit to another: joules, kilojoules, calories, kilocalories, watt-hours, kilowatt-hours, BTU, electronvolts and foot-pounds.
- Fahrenheit to Kelvin ConverterConvert Fahrenheit to kelvins or kelvins to Fahrenheit, going through Celsius with every step shown. Readings below absolute zero aren't allowed.
- Force ConverterChange a force from one unit to another: newtons, kilonewtons, dynes, pounds-force, kilograms-force, ounces-force and kips.
- Grams to Pounds ConverterConvert grams to pounds or pounds to grams with the exact 453.59237 g pound, the working shown and a grocery-weight table.
- Inch Fraction ConverterTurn millimeters, centimeters or decimal inches into the nearest tape-measure fraction of an inch, or a fraction back into decimal inches and millimeters.
- Knots to MPH ConverterConvert knots to miles per hour, or mph to knots, for boating, flying and wind forecasts, using the exact nautical mile.
- kPa to PSI ConverterConvert kilopascals to psi or psi to kPa for tire placards, weather pressure and engineering specs, with the working shown.
- Liters to Gallons ConverterConvert liters to US gallons or US gallons to liters with the exact 3.785411784 L gallon, plus fuel, water and tank examples.
- m/s to km/h ConverterConvert meters per second to kilometers per hour or km/h to m/s with the exact factor 3.6, for physics problems, wind and sport.
- Meters to Inches ConverterConvert meters to inches or inches to meters using the exact 0.0254 factor, with step-by-step working and a reference table.
- Metric Prefix ConverterMove a value between metric (SI) prefixes, from quecto to quetta. For example, microfarads to nanofarads or megahertz to gigahertz.
- Miles to Feet ConverterConvert miles to feet or feet to miles using exactly 5,280 feet per mile, with the working and a table of common distances.
- Millimeters to Centimeters ConverterChange millimeters to centimeters, or centimeters to millimeters. There are 10 mm in every cm, and you get the working and a handy table.
- Millimeters to Inches ConverterConvert millimeters to inches or inches to millimeters with the exact 25.4 factor, including fractional-inch sizes in the table.
- Number to Words ConverterSpell out any number in US English words. Decimals can be read digit by digit or as tenths and hundredths, or written the way you'd write them on a check.
- Ounces to Grams ConverterConvert ounces to grams or grams to ounces using the exact avoirdupois ounce, with the working and a kitchen-scale reference table.
- Ounces to Pounds ConverterConvert ounces to pounds or pounds to ounces using the exact 16-ounce pound, with the working and a reference table.
- Pints to Milliliters ConverterConvert US pints to milliliters or milliliters to pints, with the exact US pint and the larger British pint explained.
- Power ConverterConvert power between watts, kilowatts, megawatts, mechanical and metric horsepower, BTU per hour, foot-pounds per second and kilocalories per hour.
- Pressure ConverterChange a pressure from one unit to another: pascals, kilopascals, bar, atmospheres, psi, millimeters or inches of mercury, and torr.
- PSI to Bar ConverterChange a pressure from psi (pounds per square inch) to bar, or from bar to psi, for tires, compressors, scuba tanks and pressure washers.
- Quarts to Liters ConverterConvert US liquid quarts to liters or liters to quarts with the exact quart size, and see why a liter is just over a quart.
- Speed ConverterConvert speeds between meters per second, kilometers per hour, miles per hour, knots and feet per second. A rough sea-level Mach figure is included too.
- Square Feet to Square Meters ConverterConvert square feet to square meters or square meters to square feet for floor plans, rooms and flooring, with the exact factor shown.
- Stone to Kilograms ConverterConvert stone to kilograms or kilograms to stone with the exact 6.35029318 kg stone, the steps shown and a body-weight table.
- Stone to Pounds ConverterConvert stone to pounds or pounds to stone using the exact 14-pound stone, with the working and a body-weight reference table.
- Tablespoons to Milliliters ConverterTurn US tablespoons into milliliters, or milliliters into tablespoons. See the exact spoon size, compared with metric and Australian spoons.
- Tablespoons to Teaspoons ConverterConvert tablespoons to teaspoons or teaspoons to tablespoons for scaling recipes, with the 3-to-1 rule and the Australian exception.
- Teaspoons to Milliliters ConverterConvert US teaspoons to milliliters or milliliters to teaspoons, using the exact US teaspoon and comparing it with the 5 mL metric spoon.
- Time Unit ConverterConvert between milliseconds, seconds, minutes, hours, days, weeks, average months, years, decades and centuries, with an hours:minutes:seconds breakdown.
- Tons to Pounds ConverterConvert US short tons to pounds or pounds to tons with the exact 2,000-pound ton, and see how it differs from long tons and metric tonnes.
- Torque ConverterChange a torque spec from one unit to another: newton meters, kilonewton meters, foot-pounds, inch-pounds, kilogram-force meters and ounce-force inches.
- Volume ConverterConvert volumes between milliliters, liters, cubic meters, US cups, gallons and spoons, imperial pints and gallons, and cubic inches or feet.
- Yards to Meters ConverterConvert yards to meters or meters to yards using the exact 0.9144 factor, with sports, fabric and track distances in the table.