Unit Converter
Need to turn centimeters into inches, kilograms into pounds, or Celsius into Fahrenheit? This unit converter handles the metric-to-imperial conversions people look up most, plus everything in between. Pick a category, choose your units, type a value, and the answer appears instantly — no button to press and no rounding surprises.
Length covers millimeters, centimeters, meters, kilometers, inches, feet, yards, and miles. Weight covers milligrams, grams, kilograms, metric tons, ounces, pounds, and stones. Temperature converts between Celsius, Fahrenheit, and Kelvin. Every result uses the exact internationally agreed conversion factors, so it is precise enough for homework, recipes, shipping labels, or workshop measurements. Use the swap button to flip the direction in one click.
How it works
Length and weight conversions go through a base unit. Each length unit is stored as an exact number of meters (1 inch = 0.0254 m, 1 mile = 1,609.344 m) and each weight unit as an exact number of kilograms (1 pound = 0.45359237 kg). Your value is multiplied by the "from" factor and divided by the "to" factor, which keeps every pairing consistent — cm to inches uses the same exact data as miles to kilometers.
Formula
For length and weight: result = value × factor(from) ÷ factor(to). Temperature scales do not share a zero point, so they use offset formulas instead: °F = °C × 9/5 + 32, °C = (°F − 32) × 5/9, and K = °C + 273.15.
Worked example
Convert 100 centimeters to inches. A centimeter is 0.01 m and an inch is exactly 0.0254 m, so 100 × 0.01 ÷ 0.0254 = 39.3701 inches. For temperature, convert 100 °C to Fahrenheit: 100 × 9/5 + 32 = 180 + 32 = 212 °F — the boiling point of water at sea level.
Frequently asked questions
How do I convert cm to inches?
Divide the number of centimeters by 2.54, because one inch is defined as exactly 2.54 centimeters. For example, 100 cm ÷ 2.54 = 39.3701 inches, and 30 cm is about 11.81 inches. To go the other way, multiply inches by 2.54. A quick mental estimate is that 10 cm is roughly 4 inches.
How many pounds is 1 kg?
One kilogram equals about 2.2046 pounds, since a pound is defined as exactly 0.45359237 kilograms. So 10 kg is 22.0462 lbs and 70 kg is about 154.3 lbs. For a fast estimate, multiply kilograms by 2.2. To convert pounds back to kilograms, divide by 2.2046 or multiply by 0.4536.
What is the formula to convert Celsius to Fahrenheit?
Multiply the Celsius temperature by 9/5 (that is, 1.8) and add 32. For example, 100 °C × 1.8 + 32 = 212 °F, and 20 °C works out to 68 °F. To convert Fahrenheit back to Celsius, subtract 32 first and then multiply by 5/9. The two scales meet at −40 degrees, where the reading is identical.
How many pounds are in a stone?
One stone equals exactly 14 pounds, or about 6.35 kilograms. Stones are still widely used for body weight in the UK and Ireland, so a person weighing 11 stone weighs 154 pounds or roughly 69.9 kg. To convert kilograms to stones, divide by 6.35029318; to convert stones to pounds, simply multiply by 14.
Are these conversion factors exact?
Yes, for length and weight. The 1959 international yard and pound agreement fixed the inch at exactly 2.54 cm and the pound at exactly 0.45359237 kg, and all related units follow from those definitions. Temperature formulas are exact too. Any rounding you see happens only in the displayed result, which is trimmed to a sensible four decimal places.