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Free Unit Converter Online
Convert common measurements across length, weight, area, volume, speed, data and temperature units with precise formulas.
By Shehzad Hussain — owner and editor of ExpTool, based in Multan, Pakistan. He builds and tests every tool on this site himself.
Measurement ConverterLength ConverterWeight ConverterTemperature ConverterUnit Conversion Calculator
Interactive Unit Converter Workspace
Process your files or inputs directly in your browser. Many workflows run locally; features that need network data or a service are identified on their tool page.
At a glance
Unit Converter — Convert common measurements across length, weight, area, volume, speed, data and temperature units with precise formulas.
Free for the core workflow, no account required. The calculation is performed locally in the browser from the values you enter.
About Unit Converter
Convert common measurements across length, weight, area, volume, speed, data and temperature units with precise formulas.
A unit converter removes manual factor calculations and helps compare measurements from different systems. Temperature uses dedicated conversion formulas while physical units use standard conversion factors. The converter handles length, mass, volume, temperature, area, speed, and data units with proper dimensional handling — temperature conversions use the correct offset formulas (°F = °C × 9/5 + 32), not simple ratios, which is where naive converters go wrong. Worked example — a 5-mile run in kilometres. The exact factor is 1 mile = 1.60934 km, so 5 × 1.60934 = 8.0467 km, usually written as 8.05 km. The reverse is just as useful: a 10 km race is 10 ÷ 1.60934 = 6.2137 miles. Temperature needs a formula, not a factor: 68 °F converts as (68 − 32) × 5 ÷ 9 = 36 × 5 ÷ 9 = 20 °C, and the reverse is 20 × 9 ÷ 5 + 32 = 68 °F. Table — the same conversions at other values: 1 mile is 1.609 km, 10 miles is 16.09 km, and a full marathon of 26.2 miles is 42.16 km; in temperature, 32 °F is 0 °C, 68 °F is 20 °C, and 100 °F is 37.78 °C; in weight, 1 kg is 2.2046 lb, so 70 kg is 154.32 lb. Before / after — before: guessing that 5 miles is “about 8 km” and that 100 °F is “about 40 °C” (it is 37.8 °C — close, but wrong enough to matter for a fever); after: the exact factor, the worked arithmetic, and the rounded answer side by side. The classic mistake is treating temperature like length: multiplying Celsius by 1.8 without subtracting 32 first gives 122.4 °F for 68 °F, which is nonsense — the offset exists because the two scales start at different zeros. The second trap is data units: a “1 TB” drive holds 1,000,000,000,000 bytes, but an operating system counts in gibibytes (1,073,741,824 bytes each), so it reports about 931 GiB and the drive looks smaller than the box promised. Sources: National Institute of Standards and Technology, “The International System of Units (SI)” (2019); International Bureau of Weights and Measures, “SI Brochure” (2019). Content last reviewed: November 2026.
Primary objective: Converts length, weight, area, volume, speed, digital data and temperature units with dedicated formulas.
Privacy assurance: The calculation is performed locally in the browser from the values you enter.
How to Use Unit Converter
- Choose the measurement category.
- Enter a value and select the source and target units.
- Review the converted value and the formula category used.
- Choose the category first — length, weight, temperature, area, volume, speed, or data — because the same word can mean different units in different categories.
- Enter the value and the source unit, then pick the target unit; check the factor shown, not just the answer.
- For temperature, remember the formula has an offset: convert with (°F − 32) × 5/9, never a plain ratio.
- For data, check whether the tool means decimal megabytes (1,000,000 bytes) or binary mebibytes (1,048,576 bytes).
- Round the answer to the precision your task needs — a recipe wants one decimal, an engineering drawing wants the full figure.
Key Use Cases & Applications
- school and engineering calculations
- international measurements
- web and product specifications
- Converting recipe measurements between metric and US customary.
- Translating engineering specs for international manufacturing.
- Converting a 5-mile race distance to kilometres for a training plan.
- Translating a US recipe’s cups and Fahrenheit into millilitres and Celsius.
- Checking why a new 1 TB drive shows only about 931 GB in the operating system.
Frequently Asked Questions
Which unit categories are supported?
The current tool supports length, weight, temperature, area, volume, speed and digital data units.
Can I convert Celsius to Fahrenheit?
Yes. Temperature conversions use the corresponding Celsius, Fahrenheit and Kelvin formulas.
Are results rounded?
The interface displays a readable number of decimal places while the underlying calculation uses the conversion factor.
Why can't I convert kilograms to liters directly?
Because mass and volume are different dimensions — the conversion needs density. A kilogram of feathers and a kilogram of lead occupy very different volumes.
What is the difference between MB and MiB?
MB is 1,000,000 bytes (decimal, used by storage makers); MiB is 1,048,576 bytes (binary, used by operating systems). That gap explains why your "1TB" drive shows ~931GB.
How precise are the results?
Conversions use full-precision factors and display sensibly rounded values. For engineering work, verify against the relevant standard.
How many kilometres is a marathon?
26.2 miles × 1.60934 = 42.16 km. The official marathon distance is 42.195 km, so the rounded conversion is 42.2 km.
Why is 68 °F equal to 20 °C?
Because (°F − 32) × 5/9 = (68 − 32) × 5/9 = 20. The 32 corrects for the different zero points of the two scales.
How many millilitres are in a US cup?
236.59 ml. A metric cup is 250 ml, so a recipe written for US cups needs the smaller figure.
What is the difference between GB and GiB?
A gigabyte is 1,000,000,000 bytes (decimal); a gibibyte is 1,073,741,824 bytes (binary). That gap is why a 1 TB drive shows about 931 GiB.
How do I convert miles per hour to km/h?
Multiply by 1.60934. A 60 mph speed limit is 96.56 km/h, usually signed as 97 km/h.
Can I convert kilograms to litres?
Not directly — mass and volume are different dimensions. You need the substance’s density: 1 kg of water is 1 litre, but 1 kg of honey is only about 0.7 litres.