Convert length, weight, temperature, volume, speed, and area units instantly. Supports US imperial and metric systems. Free unit conversion tool for USA & UK.
The US is one of only three countries (alongside Liberia and Myanmar) still using the imperial measurement system as primary, while most of the world — and virtually all science — uses metric. That means Americans frequently need to convert between systems: reading a recipe in grams when you measure in cups, buying tires in millimeters, running a 5K in kilometers, or understanding a foreign product's dimensions. This free unit converter handles every major unit category instantly — length, weight/mass, temperature, volume, area, speed, time, and more — with a full metric conversion chart for reference.
The United States tried to metricate in the 1970s but the effort was voluntary and largely unsuccessful due to the enormous cost of infrastructure conversion and public resistance. The Metric Conversion Act of 1975 made metric the "preferred system" for trade and commerce, but never mandated it. The result is a hybrid system: science, medicine, and the military use metric; everyday life, construction, and food labels use both. The National Institute of Standards and Technology (NIST) maintains official US unit standards and conversion factors.
The most common length conversions and their exact factors: 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 meter = 3.28084 feet | 1 kilometer = 0.621371 miles. Quick conversions: 5 feet = 152.4 cm | 6 feet = 182.88 cm | 100 meters = 328.08 feet | 1 mile = approx 1.6 km | a 5K run = 3.107 miles. The unit conversion factor 1 inch = 2.54 cm is exact by international agreement since 1959.
The exact conversion: 1 pound = 0.453592 kilograms. Therefore: 1 kilogram = 2.20462 pounds. Quick reference: 100 lbs = 45.36 kg | 132 lbs = 59.87 kg | 150 lbs = 68.04 kg | 175 lbs = 79.38 kg | 200 lbs = 90.72 kg | 50 kg = 110.23 lbs | 70 kg = 154.32 lbs | 80 kg = 176.37 lbs | 100 kg = 220.46 lbs. For small quantities: 1 ounce = 28.3495 grams | 1 metric ton (tonne) = 2,204.62 lbs = 1,000 kg. Metric tons are commonly used in shipping and commodities trading even in the US.
The most important unit conversion for Americans travelling or reading international weather: °C = (°F − 32) × 5/9 and °F = (°C × 9/5) + 32. Key reference points: 0°C = 32°F (water freezes) | 20°C = 68°F (comfortable room temperature) | 37°C = 98.6°F (normal body temperature) | 100°C = 212°F (water boils at sea level). Weather reference: 0°C = very cold | 10°C = cool/jacket weather | 20°C = pleasant | 30°C = hot | 40°C = very hot/dangerous. Kelvin (used in science): K = °C + 273.15.
Volume conversions are critical for cooking, fuel purchases (European gas stations sell liters), and chemistry. Key conversions: 1 US gallon = 3.78541 liters | 1 liter = 0.264172 US gallons | 1 US cup = 236.588 mL | 1 tablespoon = 14.787 mL | 1 teaspoon = 4.929 mL | 1 US fluid ounce = 29.574 mL. Note: UK/Imperial measurements differ from US — 1 UK pint = 568 mL vs US pint = 473 mL. When using UK recipes, be aware that their cup and tablespoon measurements can differ slightly from US standards.
The metric system uses prefixes to indicate powers of 10: kilo- (k) = 1,000 (so 1 km = 1,000 m) | hecto- (h) = 100 | deca- (da) = 10 | base unit (meter, gram, liter) | deci- (d) = 0.1 | centi- (c) = 0.01 (1 cm = 0.01 m) | milli- (m) = 0.001 (1 mm = 0.001 m) | micro- (μ) = 0.000001 | nano- (n) = 0.000000001. Once you understand this prefix system, converting within the metric system is pure powers of 10 — far simpler than converting between feet, inches, yards, and miles.
1 meter = 1,000 millimeters. To convert m to mm, multiply by 1,000. To convert mm to m, divide by 1,000. This conversion is extremely common in engineering, manufacturing, and construction: a standard door height of 2.032 m = 2,032 mm. Tire sizes (e.g., 205/55R16) use the section width in millimeters as the first number — 205 mm = 0.205 m wide. Our Unit Converter handles m to mm, mm to cm, cm to m, and all metric length conversions instantly.
Speed: 1 mph = 1.60934 km/h | 60 mph = 96.56 km/h | 100 km/h = 62.14 mph. Area: 1 square foot = 0.0929 m² | 1 acre = 4,046.86 m² = 0.4047 hectare | 1 square mile = 2.59 km². Pressure: 1 psi = 6,894.76 Pa | standard tire pressure 35 psi = 241.3 kPa. Energy: 1 kilocalorie (food calorie) = 4,184 joules.
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Multiply feet by 0.3048 to get meters. Or divide feet by 3.28084. Quick check: 5 feet = 1.524 m | 6 feet = 1.829 m | 10 feet = 3.048 m | 100 feet = 30.48 m. For height, a 6-foot person is 182.88 cm (1.8288 m). Use our Unit Converter for instant results without mental math.
132 pounds ÷ 2.20462 = 59.87 kg. Or multiply 132 × 0.453592 = 59.87 kg. Both methods give the same answer. Our unit converter handles lbs to kg for any weight value instantly.
Primarily historical inertia, infrastructure cost, and public familiarity. The Fahrenheit scale was established in colonial America before metrication was a global priority. Unlike the metric system, which was mandated in most countries at the government level, the US never mandated Fahrenheit-to-Celsius conversion for everyday use. Scientific and medical contexts in the US use Celsius and Kelvin. The NIST — the US standards authority — uses metric exclusively for scientific purposes. See NIST.gov/metric for official US metric information.
Disclaimer: Unit conversion values in this calculator are based on internationally defined conversion factors. While every effort is made to ensure accuracy, this tool is for general informational use only. For scientific, legal, or commercial purposes requiring high precision, consult official standards from NIST.gov or your applicable regulatory authority.
It converts common measurements across categories — length, weight/mass, volume, temperature, area and speed — between metric and imperial units.
Pick the category, enter a value in one unit, and the converter applies the exact conversion factor (for example 1 inch = 2.54 cm, 1 mile = 1.609 km, 1 kg = 2.205 lb) to show the equivalent.
Temperature uses formulas rather than simple factors: °F = (°C × 9/5) + 32, and °C = (°F − 32) × 5/9. The converter handles Celsius, Fahrenheit and Kelvin.
Yes — it uses internationally defined conversion factors, with results rounded for readability. You can rely on them for cooking, travel, study and DIY.