Unit Conversion Calculators
Every unit, both directions. Length, mass, volume, temperature, area, speed, pressure, energy, digital storage and kitchen measures — plus Roman numerals and numbers in words.
77 calculators
Most used
- Celsius to FahrenheitConvert any Celsius temperature to Fahrenheit, see the arithmetic, and get kelvin and Rankine values for the same reading.
- CM to InchesTurn any length in centimeters into inches, and see heights as feet and inches, using the exact international definition of the inch.
- KG to LBSConvert kilograms to pounds, and to pounds-and-ounces or stone-and-pounds, for body weight, gym plates, luggage and shipping.
- Length ConverterConvert any distance between metric, US customary and specialty length units, from nanometers to light-years.
- Roman Numeral ConverterConvert between Arabic numbers and Roman numerals from 1 to 3,999,999, with overline notation for large values and validation of malformed numerals.
- Temperature ConverterEnter one temperature and see it in Fahrenheit, Celsius, Kelvin and Rankine at once, with the formulas and nearby reference points.
Length & height 12
- CM to InchesTurn any length in centimeters into inches, and see heights as feet and inches, using the exact international definition of the inch.
- Feet to InchesMultiply feet by 12 to get inches. Enter decimal feet or feet plus inches, such as a height of 5 ft 7 in, and get centimeters too.
- Feet to MetersConvert feet, or feet plus inches, to meters with the exact definition of the foot, and see the answer in centimeters too.
- Height ConverterConvert a person's height between centimeters and feet-and-inches in either direction, with a height chart from 4′6″ to 7′0″.
- Inches to CMMultiply any inch measurement by 2.54 to get centimeters, with millimeters and feet-and-inches shown alongside.
- Inches to FeetDivide inches by 12 to get feet, shown both as decimal feet and as feet plus inches, with yards and centimeters as well.
- KM to MilesConvert kilometers to miles for races, road signs and maps, with feet and nautical miles shown for the same distance.
- Length ConverterConvert any distance between metric, US customary and specialty length units, from nanometers to light-years.
- Meters to FeetConvert any length in meters to decimal feet and to feet and inches, with yards shown as well.
- Miles to KMConvert statute miles to kilometers for travel, training and mapping, with meters and nautical miles shown too.
- MM to InchesConvert millimeters to decimal inches and to the nearest fraction of an inch you can find on a ruler, drill index or wrench set.
- Yards to FeetMultiply yards by 3 to get feet. See the same length in inches and meters, plus fabric cuts such as 3/8 yard in inches.
Weight & mass 11
- Avoirdupois Weight ConverterConvert everyday US and British weights — drams, ounces, pounds, stone, hundredweights and tons — to each other and to metric units.
- Grams to OuncesConvert grams to avoirdupois ounces for food, packaging and postage, with pounds-and-ounces and troy ounces for precious metals.
- Grams to PoundsDivide grams by 453.59237 to get pounds, shown as decimal pounds and as pounds and ounces, with ounces and kilograms.
- KG to LBSConvert kilograms to pounds, and to pounds-and-ounces or stone-and-pounds, for body weight, gym plates, luggage and shipping.
- Ounces to GramsConvert avoirdupois ounces to grams for cooking, baking, portions and parcels, with pounds and kilograms alongside.
- Ounces to PoundsDivide ounces by 16 to get pounds, shown both as decimal pounds and as pounds and ounces, with grams and kilograms.
- LBS to KGConvert pounds, or pounds plus ounces, into kilograms and grams, with stone and pounds shown for UK readers.
- Pounds to OuncesMultiply pounds by 16 to get ounces. Works for decimal pounds and shows grams, kilograms and pounds-and-ounces.
- Stone to KGEnter a weight in stones and pounds, the way it's said in the UK and Ireland, and get kilograms, total pounds and decimal stone.
- Troy Weight ConverterConvert precious-metal weights between troy ounces, pennyweights, grains, troy pounds, grams, tolas and ordinary ounces.
- Weight ConverterConvert any weight or mass between metric, US, British and troy units, with pounds-and-ounces and stone-and-pounds breakdowns.
Temperature 10
- Celsius to FahrenheitConvert any Celsius temperature to Fahrenheit, see the arithmetic, and get kelvin and Rankine values for the same reading.
- Celsius to KelvinAdd 273.15 to a Celsius temperature to get kelvins, the absolute scale used in chemistry, physics and engineering.
- Celsius to RankineConvert Celsius temperatures to the Rankine absolute scale used in US-customary thermodynamics, with the kelvin step shown.
- Fahrenheit to CelsiusConvert Fahrenheit readings to Celsius — body temperature, weather, thermostats or cooking — with the subtraction and division shown.
- Fahrenheit to KelvinConvert Fahrenheit readings to kelvins for physics, chemistry and engineering formulas that require absolute temperature.
- Fahrenheit to RankineAdd 459.67 to a Fahrenheit temperature to get degrees Rankine, the absolute scale for US-customary gas laws and thermodynamics.
- Kelvin to CelsiusSubtract 273.15 from a kelvin value to get degrees Celsius, for cryogenics, astronomy, lab data and lighting specs.
- Kelvin to FahrenheitTurn kelvin values from science and space news into Fahrenheit, with the Celsius step and a shortcut formula shown.
- Kelvin to RankineMultiply kelvins by 9/5 to get degrees Rankine — a pure ratio, since both scales start at absolute zero.
- Temperature ConverterEnter one temperature and see it in Fahrenheit, Celsius, Kelvin and Rankine at once, with the formulas and nearby reference points.
Area & volume 13
- Acres to Sq FtMultiply acres by 43,560 to get square feet, with square yards, square meters, hectares and an equivalent square side for picturing the land.
- Area ConverterConvert any area between square feet, square meters, acres, hectares, square miles and traditional US land units.
- Cu Ft to Cu YdDivide cubic feet by 27 to get cubic yards — the unit bulk soil, mulch, gravel and ready-mix concrete are sold in.
- Cu Yd to Cu FtMultiply cubic yards by 27 to get cubic feet, then see how many bags of mulch, soil or potting mix would match a bulk order.
- Cups to mLConvert US cups to milliliters, with fluid ounces and tablespoons, and see how the same number of cups differs under metric, UK and Japanese cup sizes.
- Gallons to LitersMultiply US gallons by 3.785411784 to get liters, and see what the same number of imperial gallons would be.
- Liters to GallonsConvert liters to US gallons, with imperial gallons and US quarts alongside, for fuel, water tanks and aquariums.
- mL to Fluid OuncesConvert milliliters to US fluid ounces for drinks, bottles, toiletries and recipes, with UK fluid ounces, cups and tablespoons too.
- Sq Ft to AcresDivide square feet by 43,560 to get acres, with the nearest eighth of an acre and the metric equivalents.
- Sq Ft to Sq MConvert floor or land area from square feet to square meters, with square yards and an equivalent square shown.
- Sq M to Sq FtConvert square meters to square feet for apartment listings, hotel rooms and office space abroad, with square yards and an equal square.
- Tbsp to TspMultiply tablespoons by 3 to get teaspoons, with milliliters and fluid ounces, cup measures in spoons and other countries' tablespoon sizes.
- Volume ConverterConvert liquid and dry volumes between US, imperial and metric units, from teaspoons and cups to cubic yards and acre-feet.
Speed, force & energy 16
- Acceleration ConverterConvert acceleration between standard gravity (g), meters and feet per second squared, gals and speed-per-second units.
- Angle ConverterConvert angles between degrees, radians, gradians, arcminutes, arcseconds, turns, milliradians, NATO mils and compass points.
- Bar to PSIConvert bar to pounds per square inch, with kPa, MPa, atmospheres and water head, plus common equipment pressures quoted in bar.
- Density ConverterConvert density between metric and US units such as kg/m³, g/cm³, lb/ft³, lb/gal and lb/yd³, with specific gravity included.
- Energy ConverterConvert energy between joules, calories, kilocalories, watt-hours, kilowatt-hours, BTU, therms, foot-pounds and electronvolts.
- Force ConverterConvert force between newtons, pound-force, kilogram-force, kilonewtons, kips, dynes and other units, and see the mass that weighs that much.
- Frequency ConverterConvert between Hz, kHz, MHz, GHz, rpm, radians per second and beats per minute, with period, wavelength and the nearest musical note.
- HP to kWConvert mechanical horsepower to kilowatts and watts, and see how the result changes under metric, electrical and boiler horsepower definitions.
- kW to HPConvert kilowatts to mechanical horsepower, with metric PS, electrical horsepower and BTU per hour, and a motor-size chart from 0.75 kW to 110 kW.
- KPH to MPHConvert kilometers per hour to miles per hour, with meters per second and the time it takes to cover one mile.
- Momentum ConverterConvert linear momentum and impulse between SI, CGS and US units such as kg·m/s, N·s, g·cm/s, lb·ft/s and lbf·s.
- MPH to KPHConvert miles per hour to kilometers per hour, with meters per second and the time it takes to cover one kilometer.
- Power ConverterConvert power between watts, kilowatts, megawatts, several kinds of horsepower, BTU per hour and tons of refrigeration.
- Pressure ConverterConvert pressure between psi, pascals, kilopascals, bar, atmospheres, mmHg, inches of mercury, torr and water-column units.
- PSI to BarConvert pounds per square inch to bar, kilopascals and atmospheres, with gauge-versus-absolute pressure and typical tire pressures.
- Speed ConverterConvert speeds between miles per hour, kilometers per hour, meters per second, knots, Mach and other units, with pace per mile and per km.
Time 4
- Hours to Days ConverterConvert hours into calendar days or 8-hour workdays, as decimal days and as days plus hours, with weeks and a quick reference table.
- Hours to Minutes ConverterConvert hours, including decimal hours like 1.5 or 7.75, into minutes, hours-and-minutes and seconds.
- Minutes to Hours ConverterConvert minutes into decimal hours, hours-and-minutes and h:mm clock format, with a chart of common values.
- Time Unit ConverterConvert durations between nanoseconds, seconds, minutes, hours, days, weeks, months, several kinds of year, decades and centuries.
Data, cooking & more 4
- Cooking Measurement ConverterConvert kitchen measures between cups, spoons, milliliters and ounces, and between cups and grams for 21 common ingredients.
- Data Storage ConverterConvert digital storage sizes with decimal (kB, MB, GB, TB) and binary (KiB, MiB, GiB, TiB) units kept clearly apart, plus bits.
- Decimal Degrees ↔ DMSConvert latitude, longitude or any angle between decimal degrees and degrees-minutes-seconds, in either direction, with hemisphere letters.
- Metric Prefix ConverterMove a value between SI prefixes such as kilo, mega, milli, micro, nano and pico for any unit, from meters and grams to hertz and farads.
Flow, torque & fuel economy 3
- Flow Rate ConverterConvert volumetric flow between gpm, L/min, L/s, m³/h, cfs, cfm, MGD and oil barrels per day, with the volume moved per hour, day and month.
- Fuel Economy ConverterConvert fuel economy between US and UK miles per gallon, liters per 100 km, kilometers per liter and gallons per 100 miles.
- Torque ConverterConvert torque between N·m, lbf·ft, lbf·in, ozf·in, kgf·m and other units, and find the power a torque produces at a given rpm.
Numbers & numerals 4
- Numbers to Words ConverterSpell out any number in US English words, including decimals, negatives, huge values, check-writing amounts and ordinal words.
- Roman Numeral CalculatorDo arithmetic with Roman numerals — addition, subtraction, multiplication and division with remainder — and get the answer as a numeral.
- Roman Numeral ConverterConvert between Arabic numbers and Roman numerals from 1 to 3,999,999, with overline notation for large values and validation of malformed numerals.
- Roman Numeral Date ConverterConvert a birthday, wedding or memorial date into Roman numerals in month-day-year, day-month-year or year-first order.
Guides
- KB, MB, GB and TB Explained: Decimal vs Binary Storage UnitsStorage units come in two systems, powers of 1,000 and powers of 1,024. Learn which is which, why your drive looks smaller, and how bits and bytes differ.
- How to Convert Celsius to Fahrenheit (Exactly and in Your Head)Multiply by 1.8 and add 32, or use a quick mental shortcut. Exact formulas both ways, accuracy of the tricks, oven and weather tables, and Kelvin.
- How to Convert Centimeters to Feet and Inches (Height and Length)Divide centimeters by 2.54 to get inches, then split into feet and inches. Step-by-step method, a height chart, the reverse conversion and fraction-of-an-inch tips.
- How to Convert Kilograms to Pounds (and Pounds to Kilograms)One kilogram is about 2.2 pounds. Exact factors both ways, a mental shortcut accurate to 0.2%, pounds-and-ounces and stone conversions, and a quick chart.
- Metric Prefixes Explained: Kilo, Mega, Milli, Micro and MoreEvery metric prefix is a power of ten. A full chart of SI prefixes, a reliable way to convert between them, and the traps with squared, cubed and binary units.