Metric vs Imperial systems
Most of the world uses the metric system (SI units). The United States, Myanmar, and Liberia primarily use the Imperial system. Understanding both is essential for international work.
Most common conversions
Length
- 1 mile = 1.60934 km
- 1 foot = 0.3048 meters
- 1 inch = 2.54 cm
- 1 yard = 0.9144 meters
Weight
- 1 pound = 0.453592 kg
- 1 ounce = 28.3495 grams
- 1 stone = 6.35029 kg
- 1 US ton = 907.185 kg
Temperature formulas
- Celsius to Fahrenheit:
(°C × 9/5) + 32 - Fahrenheit to Celsius:
(°F − 32) × 5/9 - Celsius to Kelvin:
°C + 273.15
Key temperature references
| °C | °F | What it means |
|---|---|---|
| 0 | 32 | Water freezes |
| 20 | 68 | Room temperature |
| 37 | 98.6 | Human body temperature |
| 100 | 212 | Water boils |
Digital storage
Note: There are two standards — decimal (SI) and binary (IEC):
- 1 KB = 1,000 bytes (SI)
- 1 KiB = 1,024 bytes (IEC)
- 1 GB = 1,000,000,000 bytes (SI) — used by hard drive manufacturers
- 1 GiB = 1,073,741,824 bytes (IEC) — used by operating systems
This is why a "1TB" hard drive shows as ~931 GB in Windows.
Speed
- 1 mph = 1.60934 km/h
- 1 knot = 1.852 km/h
- 1 m/s = 3.6 km/h
- Speed of light = 299,792,458 m/s
Area
- 1 acre = 4,046.86 m²
- 1 hectare = 10,000 m²
- 1 square mile = 2.59 km²
- 1 square foot = 0.0929 m²
Volume
- 1 US gallon = 3.78541 litres
- 1 UK gallon = 4.54609 litres
- 1 US fluid ounce = 29.5735 ml
- 1 cubic foot = 28.3168 litres
Common mistakes in unit conversion
Confusing mass and weight: Mass (kg, lb) measures the amount of matter. Weight is a force (Newtons). In everyday use they're interchangeable, but in science they are not.
US vs UK measurements: US cups (240 ml) ≠ UK cups (284 ml). US gallons ≠ UK gallons. Always specify which system when sharing recipes or measurements internationally.
Metric prefix confusion: 1 megabyte ≠ 1 mebibyte. Hard drives use decimal (1 MB = 1,000,000 bytes) while operating systems use binary (1 MiB = 1,048,576 bytes).
How to convert units free
- Go to Unit Converter
- Select measurement category (Length, Weight, Temperature, etc.)
- Choose input and output units
- Enter value — conversion is instant
- Click any row in the all-results panel to set it as the target unit