Metric & Imperial Unit Converter
Pick a category, choose your units, and enter a value to convert instantly — length, weight, volume, speed, or temperature, no signup.
Convert a unit
Common conversions:
| Result |
How this is calculated
Length, weight, volume, and speed each convert through a fixed base unit (meters, grams,
liters, and meters/second respectively): your value is multiplied by the "from" unit's conversion factor
to get the base amount, then divided by the "to" unit's factor. Temperature can't use a
simple multiplier because Celsius, Fahrenheit, and Kelvin have different zero points, so it converts
through Celsius using F = C × 9/5 + 32 and K = C + 273.15 (and their
inverses).
Worked examples
| 1 mile | 1.60934 km |
| 1 kilogram | 2.20462 lb |
| 1 US gallon | 3.78541 L |
| 100 km/h | 62.1371 mph |
| 98.6°F (body temp) | 37°C |
| 0°C (freezing) | 273.15 K |
US customary vs. imperial units
This tool's volume units (cup, pint, quart, gallon, fluid ounce) are the US customary definitions, not the British imperial ones — they're different sizes. A US gallon is about 3.785 L, while an imperial (UK) gallon is about 4.546 L, roughly 20% larger. If you're converting a UK recipe or fuel figure, double-check which system it's using before trusting the result.
Frequently asked questions
Why isn't there a simple multiplier for temperature?
Because Celsius, Fahrenheit, and Kelvin don't share a zero point — 0°C is 32°F, not 0°F. A pure multiplier only works for units that both start at zero at the same physical point, which is true for length, weight, and volume but not temperature.
Is a US cup the same as a metric cup?
No. A US customary cup is 236.588 mL, while some countries (Australia, for example) use a "metric cup" of exactly 250 mL. This tool uses the US customary definition; for a metric cup, use 250 mL directly.
What's the difference between a metric ton and a US ton?
A metric ton (tonne) is exactly 1,000 kg (about 2,204.6 lb). A US "short ton" is 2,000 lb (about 907.2 kg), and a UK "long ton" is 2,240 lb (about 1,016 kg) — three different weights that all get called "a ton." This tool's "t" unit is the metric ton.
What's a knot, and how does it compare to mph?
A knot is one nautical mile per hour, used in aviation and marine navigation instead of mph or km/h because a nautical mile is tied to a minute of latitude, which makes chart navigation math simpler. One knot is about 1.15 mph (1.852 km/h) — slightly faster than a "regular" mile per hour despite sounding similar.
Why does swapping units sometimes show a slightly different number when I convert back?
Displayed results are rounded for readability, so converting a rounded result back to the original unit can drift by a tiny amount. The underlying math is exact; only the display is rounded.