How unit conversion works
Most unit conversions work through a fixed factor relative to a base unit. The value you type is first converted to the category's base unit (meter, kilogram, liter, km/h or square meter), then transformed into the target unit by multiplying or dividing by the matching factor.
Length
The base unit is the meter. Some common factors: 1 in = 0.0254 m, 1 ft = 0.3048 m, 1 yd = 0.9144 m and 1 mi = 1,609.344 m. To convert meters to feet, divide the value by 0.3048.
Weight and mass
The base unit is the kilogram. One pound equals 0.45359237 kg, and one ounce equals 0.028349523125 kg. To convert kilograms to pounds, divide the value by 0.45359237 (or multiply by approximately 2.20462).
Volume
The base unit is the liter. A US gallon equals 3.785411784 liters, and a cup equals 0.2365882365 liters. These measures vary between countries, so it's worth checking whether a recipe or spec uses the US standard or another system.
Temperature
Temperature doesn't follow a fixed factor, it uses its own formulas. Celsius to Fahrenheit: F = C × 9/5 + 32. Fahrenheit to Celsius: C = (F − 32) × 5/9. Celsius to Kelvin: K = C + 273.15.
Speed and area
For speed, the base unit is km/h, where 1 m/s equals 3.6 km/h and 1 knot equals 1.852 km/h. For area, the base unit is the square meter, where 1 hectare equals 10,000 m² and 1 acre equals approximately 4,046.86 m².