Unit converter
Convert length, mass, temperature, area, volume and speed.
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How we handle your data →How to use this tool
- Choose length, mass, temperature, area, volume or speed.
- Select source and destination units and enter a value without thousands separators.
- Check the output symbol and the gallon or ounce definition when relevant.
An example you can verify
Express a measurement in another unit of the same quantity.
Example input
Value: 1 From: in To: mm
Expected result
25.4 mm.
Choose the quantity before units. US and UK gallons are not the same volume.
Unit converter: uses and practical guidance
Converting units expresses the same quantity on another scale. The tool covers length, mass, temperature, area, volume and speed. Select the quantity first, followed by source and destination units. Conversion does not change the measured object: two metres and two hundred centimetres describe the same length. A number without its unit is insufficient to choose a conversion or interpret the output, so retain that context throughout the workflow.
Area and volume conversions do not use the same factor as the corresponding length conversion. One square metre contains ten thousand square centimetres because two dimensions contribute. Temperature also has a special case: Celsius and Fahrenheit differ by an offset as well as a scale. A simple proportion is therefore not appropriate for every quantity. The tool applies the definitions for its supported units instead of treating all conversions identically.
Inspect similarly named units carefully. US and UK gallons have different capacities. The supported mass ounce is neither a fluid ounce nor a troy ounce. Identify the source definition when copying a value from a recipe, specification or instrument. Temperature validation also considers absolute zero. Output rounding matters when comparing a conversion followed by its reverse; a slightly different displayed final number can reflect representation rather than a different physical quantity.
Check the destination symbol and keep it attached when copying the result. Try a familiar equivalence to detect an accidental unit selection. Average speed calculates from distance and elapsed time, while Rule of three scales proportional quantities. When a context requires measurement tolerances or precision, remember that converting units does not improve the accuracy of the original measurement or supply information that was never measured.
A practical check before using the result
To verify conversion, retain one simple equivalence and another containing decimals. Convert both in the same direction as the actual measurement and inspect the output symbol. Identify the definition behind an abbreviated source unit before selecting it. Do not mix mass and volume merely because similar names appear in a recipe; relating them may require density information not requested here. Round at the final stage when chaining calculations. Copying a heavily rounded intermediate value can introduce another difference. A useful reference combines quantity, unit and source precision so meaning survives the exchange. Check that the receiving document includes all three rather than preserving only the converted number.
Settings and limits
Choose a quantity, units and value. Inches, feet, miles and pounds use international definitions; US and UK gallons are separate. Results are rounded to 13 significant digits.
Frequently asked questions
Which ounce is used?
The avoirdupois mass ounce: 28.349523125 grams. It is not a troy ounce or a fluid ounce.
Is it free, and do I need to sign up?
Yes, it is free. You do not need to sign up, create an account or install an app, and there is no daily quota: open the tool and use it. The only limits are file sizes, which protect your device’s memory.
Is my data sent to any server?
No. What you type or paste is processed in your browser’s memory and is not sent to any server. You can check it in the browser’s Network tab or by going offline after the page has loaded.