Unit converter
Length, area, volume, mass, pressure, energy, power, speed and temperature. Enter once, read every unit in the category.
Convert
| Millimetre | 1,000 |
|---|---|
| Centimetre | 100 |
| Metre | 1 |
| Kilometre | 0.001 |
| Inch | 39.3701 |
| Foot | 3.2808 |
| Yard | 1.0936 |
| Mile | 0.00062137 |
Every factor here is a definition
None of these numbers were measured, so none of them can be revised. The international foot is exactly 0.3048 metres by agreement, the pound exactly 0.45359237 kilograms, the calorie exactly 4.184 joules. That is why a converter is one of the few tools that can be written once and left alone.
Where a unit is defined against other units rather than against an SI base, the factor is stored as the product that defines it. A pound per square inch is a pound-force over a square inch, so it is written as (0.45359237 × 9.80665) ÷ 0.0254², not as a rounded 6894.76. Storing the derivation rather than the rounded result is what stops a chain of conversions drifting.
Two that catch people out
Temperature is not a ratio. Twenty degrees is not twice ten, because the scales have offsets as well as different sizes. It is converted through kelvin here rather than by multiplying.
Horsepower is two different units. Mechanical horsepower is 550 foot-pounds per second, about 745.7 W. Metric horsepower, the PS you see on vehicles sold in Nepal, is 735.5 W. Both are listed because confusing them misreads an engine by nearly 1.5%.
Tola
Included under mass because gold in Nepal is still priced by it. One tola is 11.6638038 grams, which is the old British Indian rupee coin weight, and it is exact rather than approximate.