Tools

Unit Conversion Calculators

A unit conversion is a multiplication, which is why there are ten thousand converters on the internet and most of them are fine. The ones that are not fine are the ones that quietly pick a definition: a US gallon is not an imperial gallon, a US fluid ounce is not a UK one, and a gigabyte has meant two different things since hard drive marketing and operating systems went their separate ways.

These converters name the definition every time, and the factors come from NIST Special Publication 811 rather than from another converter. Temperature gets its own treatment, because it is the one family here that is an offset and not a factor — 0 °C is not zero anything.

All 15 unit conversion tools

Length, weight, temperature, volume, and eleven more unit families.

LengthMetres, feet, inches, miles, and nine more length units.Weight & MassKilograms, pounds, stones, ounces, and tonnes.TemperatureCelsius, Fahrenheit, and Kelvin — an offset, not just a factor.VolumeLitres, gallons, cups, and the US-versus-imperial gap.AreaSquare metres, square feet, acres, and hectares.SpeedMiles per hour, kilometres per hour, knots, and metres per second.Time UnitsSeconds through years, with exact rather than rounded months.Data StorageBytes to terabytes, decimal (GB) and binary (GiB) both.PressurePascals, bar, psi, atmospheres, and millimetres of mercury.EnergyJoules, calories, kilowatt-hours, and British thermal units.AngleDegrees, radians, gradians, and degrees-minutes-seconds.Fuel EconomyUS mpg, imperial mpg, and litres per 100 km — a reciprocal, not a factor.Number BaseBinary, octal, decimal, hex, and every base from 2 to 36.Roman NumeralsArabic to Roman and back, with the subtractive rules applied.Cooking MeasurementsCups, grams, and millilitres — by ingredient, because density differs.

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