Unit Converters
Free converters for length, weight, temperature, area, speed and pressure, in metric and US customary units.
6 calculators each one also works as a widget
- Length Converter Convert inches, feet, meters, miles and other units of length.
- Temperature Converter Convert between Celsius, Fahrenheit and Kelvin.
- Area Converter Convert square feet, square meters, acres, hectares and other units of area.
- Pressure Converter Convert psi, bar, atm and other units of pressure.
- Speed Converter Convert mph, km/h, knots and other units of speed.
- Weight Converter Convert pounds, ounces, kilograms, grams and other units of weight and mass.
Pick the Converter for What You Measure
Choose by the quantity: the Length Converter for inches, feet, meters and miles, the Weight Converter for pounds, ounces, kilograms and grams, and the Temperature Converter for Celsius, Fahrenheit and Kelvin. The Area, Speed and Pressure converters cover square feet and acres, mph and km/h, and psi and bar.
A Few Conversions Worth Remembering
One inch is exactly 2.54 centimeters and one pound is exactly 0.45359237 kilograms, because both units are defined that way. A mile is 1.609344 kilometers.
Temperature is the odd one out. The scales start from different zero points, so one multiplication is not enough: to turn Celsius into Fahrenheit, multiply by 9/5 and then add 32. That makes 20 °C equal to 68 °F. The Temperature Converter applies the right formula for each pair of scales.
Metric and US Units Side by Side
For weight, 1 kilogram is about 2.2 pounds, and 1 ounce is about 28.35 grams. For area, one hectare is 10,000 square meters, about 2.47 acres, and one acre is about 4,047 square meters. For speed, 1 knot is exactly 1.852 km/h, which sailors and pilots use, and 60 mph is about 96.6 km/h.
For pressure, 1 bar is 100,000 pascals and standard air pressure at sea level is 1 atm, which is 101,325 pascals or about 14.7 psi. Tire gauges in the US read psi, while European pumps often show bar, so the Pressure Converter is handy at the gas station.
Rounding Converted Values
Most conversion factors are long decimals, so converted values are usually rounded. Round to the precision you started with: a length measured to the nearest centimeter does not become more exact by being shown to six decimal places in inches.
Miles and Nautical Miles
A nautical mile is longer than a regular (statute) mile: it is exactly 1,852 meters, against 1,609.344 meters for a mile. Ships and aircraft use it because one nautical mile matches one minute of latitude, and a knot is one nautical mile per hour. The Length Converter lists both, so pick the right one when a distance comes from a chart or a flight plan.
Frequently Asked Questions
How do I convert Celsius to Fahrenheit?
Multiply by 9/5 (or 1.8) and add 32. For example, 25 °C × 1.8 + 32 = 77 °F. To go back, subtract 32 and multiply by 5/9.
How many centimeters are in an inch?
Exactly 2.54. So 12 inches, one foot, is 30.48 cm.
What is the difference between weight and mass?
Mass is how much matter something has. Weight is the force of gravity on that mass. In everyday use both words mean the same thing, and the Weight Converter converts mass units such as kilograms, pounds and ounces.