Instantly convert between metric and imperial units for length, weight, temperature, area, volume, speed, and data
| Unit | Value |
|---|
Understanding the two main measurement systems used around the world
International System of Units
Prefixes make scaling easy:
milli (÷1000) · centi (÷100) · kilo (×1000) · mega (×1,000,000)
Traditional measurement system
Notable quirk:
UK uses imperial for miles and pints but metric for most other official measurements
Length
1 inch = 2.54 cm
1 mile = 1.609 km
1 foot = 30.48 cm
Weight
1 lb = 453.6 g
1 kg = 2.205 lbs
1 oz = 28.35 g
Temperature
0°C = 32°F
100°C = 212°F
37°C = 98.6°F
Volume
1 gal = 3.785 L
1 fl oz = 29.57 mL
1 cup = 236.6 mL
Speed
1 mph = 1.609 km/h
1 knot = 1.852 km/h
1 m/s = 3.6 km/h
Area
1 acre = 0.405 ha
1 sq mi = 2.59 km²
1 sq ft = 0.0929 m²
Common questions about unit conversion
To convert kilometres to miles, multiply the number of kilometres by 0.621371. For example, 10 kilometres equals 6.21371 miles. Alternatively, divide the kilometres by 1.60934.
A useful mental shortcut: multiply by 0.6 for a quick estimate. So 100 km is approximately 60 miles (actual: 62.1 miles). Use the converter above for precise results — select Length, enter your value in kilometres, and choose miles as the target unit.
Use the formula: F = (C × 9/5) + 32. For example, 100°C = (100 × 1.8) + 32 = 212°F.
For a quick mental estimate, double the Celsius temperature and add 30. This gives an approximation (e.g., 20°C → 40 + 30 = 70°F; actual is 68°F).
Key reference points: 0°C = 32°F (freezing) · 20°C = 68°F (room temp) · 37°C = 98.6°F (body temp) · 100°C = 212°F (boiling).
The metric system (SI) is a decimal-based system used by most of the world. All conversions are powers of 10, making calculations straightforward. Units: metres, kilograms, litres, Celsius.
The imperial system (used primarily in the US, and partially in the UK) uses irregular conversion factors — 12 inches in a foot, 16 ounces in a pound, 5,280 feet in a mile. This makes mental arithmetic more challenging.
The metric system is the global standard in science, medicine, and international trade. The US remains the most notable exception, though science and medicine in the US also use metric.
In computing, 1 gigabyte (GB) = 1,073,741,824 bytes using the binary (base-2) definition (1024³), which is how operating systems measure file sizes.
Hard drive manufacturers use the decimal definition where 1 GB = 1,000,000,000 bytes. This ~7% discrepancy is why a "1 TB" drive shows up smaller in Windows or macOS.
Our converter uses the binary standard: 1 KB = 1,024 bytes · 1 MB = 1,048,576 bytes · 1 GB = 1,073,741,824 bytes · 1 TB = 1,099,511,627,776 bytes.
A nautical mile is exactly 1,852 metres (approximately 1.15078 statute miles or 6,076.1 feet). It is used in maritime and aerial navigation.
The nautical mile is based on the Earth's circumference: one nautical mile equals one minute of arc of latitude. This makes it ideal for navigation, since latitude lines on charts correspond directly to nautical miles.
Speed at sea and in aviation is measured in knots, where 1 knot = 1 nautical mile per hour. A ship travelling at 20 knots covers 20 nautical miles (37.04 km) in one hour.
This unit converter is provided for informational and educational purposes. Conversion factors are based on internationally recognised standards (SI, NIST). Results are computed client-side in your browser — no data is sent to any server. For mission-critical applications in engineering, legal, medical, or scientific contexts, always verify conversions with certified reference sources. © 2026 ShortcutCircle.