Unit Converters
Metric and US customary conversions using exact defined factors, with US and imperial measures kept apart.
Calculators
- Length Converter
Metric and US customary lengths, from millimeters to miles.
- Area Converter
Square meters, square feet, acres, hectares and more.
- Volume Converter
Liters, cubic units and cooking measures, keeping US and imperial units separate.
- Weight (Mass) Converter
Kilograms, pounds, ounces, stones and tons, with short and long tons distinguished.
- Temperature Converter
Celsius, Fahrenheit and Kelvin readings, and temperature differences.
- Speed Converter
km/h, mph, m/s, knots and feet per second.
- Pressure Converter
Pascals, bar, psi, atmospheres, mmHg and inches of mercury.
- Energy and Power Converter
Joules, calories, kWh and BTU; watts and horsepower — kept as separate quantities.
- Data Storage and Transfer Time Calculator
Bits and bytes with decimal (MB) and binary (MiB) prefixes, plus download time.
Picking the right converter
The converters use exact defined factors wherever they exist, so the only rounding is the number of digits you choose to show. What matters most is choosing the right unit, especially where two units share a name.
- Length, area or volume?
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Length Converter Area Converter Volume Converter
Metric and US customary units, feet-and-inches entry, and US and imperial gallons and fluid ounces kept apart.
- Weight?
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Grams, kilograms, ounces, pounds and stones, with troy ounces labeled for precious metals.
- Temperature?
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Readings and differences are converted separately: 10 °C is 50 °F, but a rise of 10 °C is a rise of 18 °F.
- Speed, pressure, energy or power?
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Speed Converter Pressure Converter Energy and Power Converter
Road, running and marine speeds; gauge and absolute pressure; and energy and power kept as the separate quantities they are.
- File sizes and download times?
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Data Storage and Transfer Time Calculator
Decimal and binary prefixes side by side, and transfer time at a given connection speed.
Have these to hand
- The unit exactly as printed on the label, gauge or specification sheet.
Mistakes that change the answer
- Using a US gallon where a figure is in imperial gallons. The imperial gallon is about 20% larger.
- Converting a temperature change with the reading formula, adding 32 where it does not belong.
- Expecting a drive sold as 1 TB to show 1,000 GB on a system that counts in binary units. It shows about 931.
- Treating kilowatts, a rate, as kilowatt-hours, an amount.
Related guides
- Unit conversion pitfalls: gallons, tons, cups, GB vs. GiB
Nine unit traps with the numbers worked out: US vs. imperial gallons and pints, fluid ounces vs. ounces, three kinds of ton, cups of flour in grams, cup and tablespoon sizes, GB vs. GiB, bits vs. bytes, temperature changes and UK vs. US mpg.
- How to measure a room for square footage and volume
Measure, convert inches to decimal feet, split odd shapes into rectangles, then multiply and convert with a squared or cubed factor. Worked with an L-shaped room, a concrete pad and a water tank.
- How much extra flooring, tile, paint and concrete to buy
Published rules of thumb for overage by material and layout, what each one covers, and worked examples that apply the allowance first and round up to whole boxes, cans and bags last.