Converters calculators
Six unit converters built on exact, internationally defined factors — including the three conversions that are not simple multiplication.
All six unit converters
Length Converter
Convert m, cm, mm, km, in, ft, yd, mi.
Open tool →Weight Converter
Convert kg, g, lb, oz, stone.
Open tool →Temperature Converter
Celsius, Fahrenheit, and Kelvin.
Open tool →Speed Converter
mph, km/h, m/s, knots.
Open tool →Area Converter
m2, ft2, acres, hectares, yd2.
Open tool →Data Storage Converter
KB, MB, GB, TB (decimal SI).
Open tool →Three of these are not simple multiplication
Most unit conversion is one multiplication: pick the factor, apply it, done. That is exactly how length, weight and speed work here. Three of the six behave differently, and that is where hand calculations go wrong.
- Temperature has an offset, not just a scale. Celsius and Fahrenheit disagree about both the size of a degree and where zero sits, so the conversion has two steps. Doing one and forgetting the other is the single most common conversion error there is.
- Area factors are squared. A foot is 0.3048 m, so a square foot is 0.3048², or 0.0929 m² — not 0.3048 m². People reuse the linear factor and land a factor of three away from the right answer.
- Data storage has two competing conventions. Drive manufacturers count in powers of ten, operating systems count in powers of two, and the gap is why a 1 TB drive reports as 931 GB. Nothing is missing; the two sides are counting differently.
Exact factors, not approximations
Where a conversion factor is defined by international agreement rather than measured, these converters use the exact value. An inch is exactly 25.4 mm. A pound is exactly 0.45359237 kg. A mile is exactly 1609.344 m. These are definitions, not measurements, so there is no rounding error to accumulate and no reason to use the approximations you may have memorised.
The practical upshot is that answers stay precise through chained conversions. Going from miles to metres to feet will not drift, because every step is exact.
Bits, bytes and other traps
One last thing worth knowing before you use the storage converter: internet connections are quoted in bits per second and files are measured in bytes. Eight bits make a byte, so a 100 Mb/s line delivers about 12.5 MB/s. A download that seems eight times slower than advertised is usually this, not a fault.