How to use this calculator
Select length, mass, or temperature, then choose a source and target unit in the same category. Length is based on meters and mass on kilograms. Temperature uses offset formulas, not just multiplication. Swap units to reverse a calculation without reusing a rounded result.
The formula
Length and mass: result = value × source factor ÷ target factor. K = °C + 273.15. °F = °C × 1.8 + 32.
A worked example
1 inch = 2.54 centimeters. 1 foot = 0.3048 meters. 1 pound = 0.45359237 kilograms. 1 ounce = 0.028349523125 kilograms. 32°F = 0°C = 273.15 K. At absolute zero, 0 K = −273.15°C.
What to keep in mind
- Length: mm, cm, m, km, in, ft. Mass: g, kg, oz, lb. Negative length and mass are not accepted.
- Temperatures must be at or above absolute zero: 0 K, −273.15°C, or −459.67°F.
- 1 in = 0.0254 m; 1 ft = 0.3048 m; 1 lb = 0.45359237 kg; 1 oz = 0.028349523125 kg. These are exact definitions. Ounces are avoirdupois, not fluid or troy ounces.
Definitions and sources
Formula v1.0.0 · Updated November 6, 2026 · Results: up to 6 decimal places, rounded half up. Very small nonzero values use scientific notation.