Unit Converter (Length, Mass, Volume, Temperature)
Convert between metric and imperial units for length, mass, volume, and temperature. Fast, accurate, and works with any value.
What this calculates
A general-purpose unit converter for the four most common categories: length (meters, feet, miles…), mass (kilograms, pounds, ounces…), volume (liters, gallons, cups…), and temperature (Celsius, Fahrenheit, Kelvin). All conversions are exact (or to standard precision for floats) and use SI definitions.
Formula & how it works
Length, mass, and volume are linear conversions: target = source × factor. Common factors: 1 inch = 2.54 cm, 1 lb = 0.4535924 kg, 1 US gallon = 3.785412 L. Temperature is affine: °F = °C × 9/5 + 32, K = °C + 273.15. Going the other way: °C = (°F − 32) × 5/9.
Worked example
100 km = 100 × 0.621371 = 62.14 miles. 70 kg = 70 × 2.20462 = 154.32 lb. 1 US gallon = 3.785 L = 16 cups. 100 °F = (100 − 32) × 5/9 ≈ 37.78 °C — normal-but-warm body temperature.
Frequently asked questions
Why is US vs UK gallon different?
Pre-1824 the British 'imperial gallon' was redefined to 4.546 L; the US kept the older 3.785 L wine gallon. Same word, different volume. UK pints, quarts, and ounces all differ from US versions accordingly.
Are ounces of weight and volume the same?
No. A fluid ounce (volume) is roughly 29.6 mL; an ounce of weight (mass) is 28.35 g. They're equal only for substances with the same density as water, and only coincidentally.
Why is temperature different?
Length and mass scales are zero-based (0 m = 0 ft), so a single multiplier works. Temperature scales have offset zero points (0 °C ≠ 0 °F), so an addition step is needed too. Kelvin shares Celsius's scale but starts at absolute zero.
How precise are these conversions?
Internally we use the full-precision constants (e.g., 1 inch = exactly 25.4 mm). Display rounds to 4 decimal places for readability — increase precision in your head if the application demands it.