Unit Converter
Convert length, mass, area, volume, time, speed, energy, pressure, power, data, and temperature.
Written by Golam Rabbani, Founder & Lead Engineer
How to use this unit converter
- Pick a category — length, mass, area, volume, time, speed, energy, pressure, power, digital data, or temperature.
- Choose From and To units from the dropdowns.
- Type the value to convert.
- Use the swap (⇄) button to flip From and To without re-typing.
- Press Convert to see the result and Copy to send it to your clipboard.
About this unit converter
The unit converter handles eleven measurement categories with conversion factors taken straight from NIST Special Publication 811 and ISO 80000. Every linear conversion uses an exact factor: 1 in = 0.0254 m, 1 lb = 0.45359237 kg, 1 ft² = 0.09290304 m², 1 mile = 1609.344 m, 1 cal = 4.184 J, 1 atm = 101,325 Pa. Temperature is handled separately because Celsius and Fahrenheit are affine — they have non-zero offsets — so the tool routes °F ↔ °C through Kelvin to avoid the off-by-32 mistakes that plague hand conversions.
Worked example: converting 5 miles to kilometres. 1 mile = 1609.344 m exactly, and 1 km = 1000 m, so 5 × 1609.344 ⁄ 1000 = 8.04672 km. Or 100 °F to Celsius: (100 − 32) × 5⁄9 = 37.78 °C. Or 1 GB to gibibytes (the binary one): 1 GB = 10⁹ B, 1 GiB = 2³⁰ B = 1,073,741,824 B, so 1 GB = 10⁹ ⁄ 2³⁰ ≈ 0.9313 GiB — exactly the discrepancy that makes a "1 TB" drive show as 931 GiB in the operating system.
FAQ
- How accurate are the conversions?
- Exact. Every factor comes from NIST SP 811 or ISO 80000 and is stored to full precision. The only rounding is on display (six decimal places by default).
- Why do US and imperial pints differ?
- They have different histories. 1 US pint = 16 US fl oz = 473.18 mL; 1 imperial (UK) pint = 20 imp fl oz = 568.26 mL. The tool keeps US and UK liquid units in separate categories so you never silently mix them.
- What about binary vs decimal data sizes?
- Both are included. kB / MB / GB / TB use powers of 10; KiB / MiB / GiB / TiB use powers of 2 (per IEC 80000-13). 1 GiB = 1024³ bytes; 1 GB = 10⁹ bytes.
- How is temperature handled?
- Via Kelvin. The tool converts the input to K first, then to the target unit — so °F ↔ °C and °C ↔ K and °F ↔ K all use a single, consistent affine map.
- Can I convert between categories (e.g., mass to volume)?
- No — that requires a density, which is substance-specific. Keep mass and volume separate, or use a dedicated tool that knows the substance.
- Is the unit converter free?
- Yes — free, no signup, no usage cap, runs entirely in your browser.