Metric vs. Imperial: Which Countries Use Which?
The United States, Liberia, and Myanmar are the only countries still primarily using the Imperial system for everyday measurements. Everywhere else uses the metric (SI) system. This creates constant friction for travelers, scientists, cooks, and engineers.
Our free unit converters handle all the math instantly.
Temperature Conversion
The three common temperature scales:
- Celsius (°C): Water freezes at 0°C, boils at 100°C. Used everywhere except the US.
- Fahrenheit (°F): Water freezes at 32°F, boils at 212°F. Used in the United States.
- Kelvin (K): Absolute scale used in science. 0 K = absolute zero = -273.15°C.
Key formulas:
- °C to °F: (°C × 9/5) + 32
- °F to °C: (°F − 32) × 5/9
- °C to K: °C + 273.15
Useful references: 0°C = 32°F (freezing) | 20°C = 68°F (room temp) | 37°C = 98.6°F (body temp) | 100°C = 212°F (boiling)
Length Conversion
The metric system is based on powers of 10, making conversions straightforward. Imperial units are historical accidents with arbitrary ratios.
| Metric | Imperial Equivalent | |---|---| | 1 kilometer | 0.621371 miles | | 1 meter | 3.28084 feet / 39.3701 inches | | 1 centimeter | 0.393701 inches | | 2.54 centimeters | 1 inch (exact) | | 1.60934 kilometers | 1 mile | | 0.9144 meters | 1 yard |
Weight & Mass Conversion
Note: Weight and mass are technically different (weight depends on gravity), but in everyday use they are interchangeable on Earth.
| From | To | Multiply by | |---|---|---| | Kilograms | Pounds | 2.20462 | | Pounds | Kilograms | 0.453592 | | Grams | Ounces | 0.035274 | | Ounces | Grams | 28.3495 | | Metric tons | US tons (short) | 1.10231 |
Digital Storage Conversion
Digital storage uses two parallel systems: decimal (used by hard drive manufacturers) and binary (used by operating systems). This is why a "1TB" hard drive shows as ~931 GB in Windows.
| Binary (IEC) | Decimal (SI) | |---|---| | 1 KiB = 1,024 bytes | 1 KB = 1,000 bytes | | 1 MiB = 1,048,576 bytes | 1 MB = 1,000,000 bytes | | 1 GiB = 1,073,741,824 bytes | 1 GB = 1,000,000,000 bytes | | 1 TiB = 1.0995 × 10¹² bytes | 1 TB = 10¹² bytes |
Speed Conversion
Common speed conversions:
- 1 mph = 1.60934 km/h
- 1 m/s = 3.6 km/h = 2.23694 mph
- 1 knot = 1.852 km/h = 1.15078 mph
- Mach 1 ≈ 1,235 km/h ≈ 767 mph (at sea level, 15°C)
Quick Reference: Common Conversions to Memorize
- 1 inch ≈ 2.5 cm (exact: 2.54)
- 1 kg ≈ 2.2 lbs
- 1 mile ≈ 1.6 km
- 1 liter ≈ 0.26 US gallons
- 0°C = 32°F | 100°C = 212°F