The conversion idea
Most unit conversions multiply by a fixed factor that relates one unit to another through a shared base unit. For example, length conversions often use metres as the common base.
value_in_to = value_in_from × (factor_from ÷ factor_to)
Temperature is different because Celsius, Fahrenheit and Kelvin are related by formulas, not a single proportional factor alone.
Useful length factors (exact or standard)
- 1 inch = 0.0254 m
- 1 foot = 0.3048 m
- 1 mile = 1609.344 m
- 1 km = 1000 m
Examples
Length: Convert 1 metre to feet.
1 ÷ 0.3048 ≈ 3.2808 ft
Weight: Convert 1 kilogram to pounds (1 lb ≈ 0.45359237 kg).
1 ÷ 0.45359237 ≈ 2.2046 lb
Temperature: Convert 25°C to Fahrenheit.
F = C × 9/5 + 32 = 25 × 1.8 + 32 = 77°F
Temperature: Convert 32°F to Celsius.
C = (F − 32) × 5/9 = 0 × 5/9 = 0°C
Tips
- Keep track of significant figures for scientific work; everyday tasks often need only a few decimal places.
- Binary data units (KiB, MiB) use powers of 1024, which differs from decimal SI kilobytes in some contexts.