Online Unit Converter
Type a value and pick your units: the conversion appears instantly, both ways, with the formula used and the result in every other unit of the category.
- 6 categories
- Instant conversion
- Formula shown
- Free
100% private — Everything is processed directly in your browser: your files, voice, and image are never sent to Chatzam's servers.
How to convert units?
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Pick the category
Length, weight, temperature, volume, area or speed.
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Enter the value
Type a number in either field and choose the units: the other field updates with every digit. The swap button switches the two units.
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Read the formula and the table
The conversion formula appears under the result, and a table gives the same value in every unit of the category.
All your everyday conversions
Metric and US/imperial
Inches, feet, miles, ounces, pounds, stone, gallons, acres or knots side by side with metric units.
Both directions
Type in one field or the other: the conversion happens instantly both ways, with no button to click.
Formula shown
Every result comes with its formula, for example °F = °C × 9/5 + 32, so you can check it or redo the math.
Full table
The value you enter is converted into every unit of the category at once, all at a glance.
Convert inches to cm, feet and miles
Since 1959, one inch has been exactly 2.54 cm. To go from inches to centimeters, multiply by 2.54; to go from centimeters to inches, divide by 2.54: a 65-inch TV has a diagonal of 165.1 cm, and 1 cm is about 0.394 inch. A foot has 12 inches, or 30.48 cm: someone who is 6 feet tall measures 182.88 cm, and 5 ft 9 in is 175.26 cm. A yard is 3 feet (91.44 cm) and a statute mile is 1.609344 km, so 100 miles is about 160.9 km. Don't confuse it with the nautical mile, used at sea and in aviation, which is 1,852 m. The tool's table shows all these equivalents at once.
Convert °F to °C and kelvin
Temperature can't be converted with a simple factor, because the scales don't share the same zero. To go from Fahrenheit to Celsius, subtract 32 and multiply by 5/9: 100 °F is (100 − 32) × 5/9 ≈ 37.8 °C, and 32 °F is 0 °C. The other way, multiply by 9/5 and add 32: 37 °C gives 37 × 9/5 + 32 = 98.6 °F, normal body temperature. The two scales meet at −40, where −40 °C = −40 °F. The kelvin, the scientific unit, has the same step size as the degree Celsius but starts at absolute zero: add 273.15, so 20 °C is 293.15 K.
Weight, volume and speed: traps to avoid
A pound (lb) is exactly 0.45359237 kg, so 1 kg is about 2.2 pounds and 150 lb is about 68 kg. The ounce used for weight is about 28.35 g, and the stone, still common in the UK for body weight, is 14 pounds, or about 6.35 kg. For volume, watch out for the gallon: a US gallon holds about 3.785 L, an imperial (UK) gallon 4.546 L. The cups and spoons in American recipes are US measures, different from metric cups used in the UK or Australia. For speed, 1 m/s is 3.6 km/h, 1 mph is 1.609344 km/h, and one knot, one nautical mile per hour, is 1.852 km/h. Driving at 70 mph is about 112.7 km/h.
Frequently Asked Questions
How many cm are in an inch?
An inch is exactly 2.54 cm. To convert inches to centimeters, multiply by 2.54; to convert centimeters to inches, divide by 2.54.
How do I convert Fahrenheit to Celsius?
Subtract 32, then multiply by 5/9. For example, 68 °F = (68 − 32) × 5/9 = 20 °C. The other way, multiply by 9/5 (or 1.8) and add 32.
How many kg are in a pound?
A pound (lb) is exactly 0.45359237 kg, or about 454 g. One kilogram is therefore about 2.2 pounds.
How many liters are in a gallon?
It depends on the country: a US gallon holds about 3.785 liters, an imperial (UK) gallon about 4.546 liters. Choose the right gallon in the list of volume units.
How many square feet are in an acre, and in a hectare?
An acre is 43,560 square feet, or about 4,047 m². A hectare is exactly 10,000 m², a square 100 m on each side, which is about 2.47 acres.