Utility
Unit Converter
Convert length, weight, temperature, volume, and more
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The World's Two Measurement Systems
The world primarily uses two systems of measurement: the metric system (formally the International System of Units, or SI) and the imperial system. The metric system is used by virtually every country in the world and by all of science and engineering globally. The United States is one of only three countries (alongside Liberia and Myanmar) that have not officially adopted the metric system for everyday use — though even the US uses metric in science, medicine, and military applications.
Length Conversion Reference
Key length conversions to memorize:
- 1 inch = 2.54 cm (exact, by definition)
- 1 foot = 30.48 cm = 0.3048 m
- 1 yard = 0.9144 m
- 1 mile = 1.60934 km
- 1 km = 0.62137 miles
- 1 meter = 3.28084 feet = 39.3701 inches
- 1 nautical mile = 1.852 km (used in aviation and navigation)
Weight (Mass) Conversion Reference
- 1 kg = 2.20462 lbs
- 1 lb = 0.453592 kg
- 1 stone (UK) = 14 lbs = 6.35 kg
- 1 metric ton = 1,000 kg = 2,204.6 lbs ≈ 1.102 short tons (US)
- 1 ounce = 28.3495 g
Temperature Conversion Formulas
Temperature conversions are non-linear (they involve an offset), making them tricky to do mentally:
- Celsius to Fahrenheit: °F = (°C × 9/5) + 32
- Fahrenheit to Celsius: °C = (°F − 32) × 5/9
- Celsius to Kelvin: K = °C + 273.15
- Kelvin to Celsius: °C = K − 273.15
Key temperature benchmarks:
- Water freezes: 0°C = 32°F = 273.15 K
- Room temperature: ~20–22°C = 68–72°F
- Human body: 37°C = 98.6°F
- Water boils: 100°C = 212°F (at sea level)
- Absolute zero: −273.15°C = −459.67°F = 0 K
Volume Conversion Reference
- 1 US gallon = 3.78541 liters = 128 fl oz
- 1 UK/Imperial gallon = 4.54609 liters
- 1 liter = 0.264172 US gallons = 33.814 fl oz
- 1 cup (US) = 236.588 ml = 8 fl oz
- 1 tablespoon = 14.787 ml = 3 teaspoons
Speed Conversion Reference
- 1 mph = 1.60934 km/h
- 60 mph = 96.56 km/h
- 100 km/h = 62.14 mph
- 1 knot = 1.852 km/h = 1.151 mph (used in aviation/maritime)
- 1 m/s = 3.6 km/h = 2.237 mph
Frequently Asked Questions
How do I convert Celsius to Fahrenheit?
The formula is: °F = (°C × 9/5) + 32. Common conversions: 0°C = 32°F (freezing point), 100°C = 212°F (boiling point), 37°C = 98.6°F (body temperature), 20°C = 68°F (room temperature), -40°C = -40°F (the point where both scales meet).
How many centimeters are in an inch?
There are exactly 2.54 centimeters in one inch. This is a defined exact value. So 1 foot (12 inches) = 30.48 cm, 1 yard (36 inches) = 91.44 cm, and 1 meter = 39.3701 inches.
How do I convert kg to lbs?
1 kilogram = 2.20462 pounds. To convert kg to lbs, multiply by 2.20462. To convert lbs to kg, divide by 2.20462 (or multiply by 0.453592). Example: 70 kg = 70 × 2.20462 = 154.3 lbs.
How many liters in a gallon?
There are approximately 3.78541 liters in a US liquid gallon. Note that the UK/Imperial gallon is larger: 1 Imperial gallon = 4.54609 liters. In the US, the liquid gallon (3.785 L) is used for most everyday purposes. The US dry gallon (4.405 L) is rarely used.
What is the difference between metric and imperial systems?
The metric system (SI) uses base units of meter, kilogram, and liter, with prefixes (milli-, centi-, kilo-) for multiples of 10. The imperial system (used mainly in the US) uses feet, pounds, and gallons, with less systematic conversion factors. Most countries use the metric system exclusively; the US uses a mix of both.
How do I convert square feet to square meters?
1 square foot = 0.092903 square meters. 1 square meter = 10.7639 square feet. Example: a 500 sq ft apartment = 500 × 0.0929 = 46.45 m². A 1,000 m² lot = 10,764 sq ft.