The Problem With Living in a World That Uses Two Measurement Systems
The United States uses miles, pounds, and Fahrenheit. The rest of the world uses kilometres, kilograms, and Celsius. As a result, anyone who reads international news, watches foreign recipe videos, buys products from overseas, follows science content, or travels internationally spends a surprising amount of time converting units.
A recipe says 200 grams of flour. Your kitchen scale shows ounces. A weather app shows 35°C. You want to know if that is hot. A product ships from the US and weighs 2.5 pounds. You want to know if that is 1 kilogram or closer to 2. These conversions happen dozens of times a week for most people who interact with content from multiple countries.
This tool converts length, weight, and temperature instantly. Type any value, select the unit, and see the converted result in real time.
—Length Conversions — The Complete Reference
Length is the most commonly converted unit type because the metric and imperial systems are used interchangeably across sports, science, construction, navigation, and everyday conversation.
Kilometres to Miles — Multiply kilometres by 0.621371. A 5km run is approximately 3.1 miles. A 100km road trip is approximately 62 miles. This is the conversion most people need most often when reading international news about distances.
Miles to Kilometres — Multiply miles by 1.60934. A 26.2-mile marathon is approximately 42.2 kilometres. A 60mph speed limit is approximately 97 km/h.
Metres to Feet — Multiply metres by 3.28084. A person who is 1.75 metres tall is approximately 5 feet 9 inches tall. A 100-metre sprint covers approximately 328 feet.
Feet to Metres — Multiply feet by 0.3048. A 6-foot person is approximately 1.83 metres. A standard ceiling height of 8 feet is approximately 2.44 metres.
Centimetres to Inches — Multiply centimetres by 0.393701. A 30cm ruler is approximately 11.8 inches. Clothing sizes in European centimetres convert to US inches using this factor.
Inches to Centimetres — Multiply inches by 2.54. A 15-inch laptop screen is approximately 38.1cm. A 12-inch pizza is approximately 30.5cm in diameter.
—Weight Conversions — The Complete Reference
Weight conversions are essential for cooking, fitness, shipping, and reading nutritional information across products from different countries.
Kilograms to Pounds — Multiply kilograms by 2.20462. A person weighing 70kg is approximately 154 pounds. A 1kg bag of rice is approximately 2.2 pounds.
Pounds to Kilograms — Multiply pounds by 0.453592. A 150-pound person weighs approximately 68 kilograms. A 5-pound bag of flour is approximately 2.27 kilograms.
Grams to Ounces — Multiply grams by 0.035274. A 100-gram serving of food is approximately 3.5 ounces. A 200-gram chocolate bar is approximately 7 ounces.
Ounces to Grams — Multiply ounces by 28.3495. A 4-ounce chicken breast is approximately 113 grams. An 8-ounce glass of water is approximately 227 grams.
Metric Tons to Pounds — Multiply metric tons by 2204.62. This conversion is used in industrial, shipping, and agricultural contexts where large quantities are measured.
—Temperature Conversions — The Formulas and What the Numbers Mean
Temperature is the most confusing unit conversion because it does not use simple multiplication — it requires both multiplication and addition or subtraction because the scales start at different zero points.
Celsius to Fahrenheit — Multiply by 9, divide by 5, then add 32. Or use the quick formula: (°C × 1.8) + 32 = °F
Examples: 0°C = 32°F (freezing point of water). 100°C = 212°F (boiling point of water). 37°C = 98.6°F (normal human body temperature).
Fahrenheit to Celsius — Subtract 32, multiply by 5, then divide by 9. Or: (°F − 32) ÷ 1.8 = °C
Examples: 32°F = 0°C. 98.6°F = 37°C. 350°F = 177°C (common baking temperature).
Celsius to Kelvin — Add 273.15. Kelvin is used in science and engineering. 0K is absolute zero — the coldest possible temperature. 0°C = 273.15K. 100°C = 373.15K.
Temperature Reference Points Everyone Should Know
Below 0°C / 32°F — Freezing. Water turns to ice. Roads become dangerous.
10°C / 50°F — Cold. Jacket weather in most climates.
20°C / 68°F — Comfortable room temperature.
30°C / 86°F — Hot. Most people begin to feel uncomfortable outdoors.
37°C / 98.6°F — Normal human body temperature.
40°C / 104°F — Dangerously hot. Heat stroke risk for prolonged outdoor exposure.
100°C / 212°F — Boiling point of water at sea level.
—Everyday Situations Where You Need These Conversions
International recipes — European recipes use grams and Celsius. American recipes use cups, ounces, and Fahrenheit. Converting between them is essential for anyone who cooks from international sources.
Fitness and health — Running distances are measured in kilometres in most countries and miles in the US. Body weight is measured in kilograms in medical contexts globally but in pounds in everyday US usage. Understanding both systems helps when following international training plans or reading health research.
Travel — Speed limits in kilometres, distances in kilometres, temperatures in Celsius — all need converting for US travellers. Luggage weight limits at airports are often in kilograms for international flights and pounds for domestic US flights.
Online shopping — Product dimensions and weights from international sellers are almost always in metric units. Knowing whether a 500-gram package is half a kilogram or more helps make informed purchasing decisions.
—Frequently Asked Questions
Why does the US still use imperial units?
Historical inertia, infrastructure cost of conversion, and public resistance to change. The US has attempted metrication several times — most notably with the Metric Conversion Act of 1975 — but adoption has been voluntary and incomplete. Scientific and medical contexts in the US use metric units. Everyday life largely does not.
What is the easiest way to mentally convert Celsius to Fahrenheit?
Double the Celsius temperature and add 30 for a quick mental estimate. This gives an approximate answer fast enough for practical use. For example, 20°C: double is 40, add 30, estimate 70°F. The actual answer is 68°F — close enough for everyday purposes.
How many centimetres are in an inch exactly?
Exactly 2.54 centimetres per inch. This is an exact defined value, not an approximation. The inch is officially defined as 25.4 millimetres.
What is the difference between mass and weight?
Mass is the amount of matter in an object and does not change regardless of location. Weight is the force of gravity acting on mass and varies depending on gravitational field strength. On the moon, your mass is the same as on Earth but your weight is about one-sixth. In everyday use, people use weight and mass interchangeably even though they are technically different quantities.
Is this tool free?
Yes, completely free with no account required. All conversions happen instantly in your browser.
—Type It In. Get the Answer. Done.
Select your conversion type — length, weight, or temperature. Enter the value you have. The converted result appears instantly. No formulas to remember, no manual calculations, no unit confusion.