📏 Unit Converter

Convert between units for length, weight, temperature, data, and more

✓ Free Forever · ✓ No Signup · ✓ No Upload · ✓ Works Offline

🔒 Your data never leaves your device. All processing happens locally in your browser using JavaScript calculation engine. No upload, no server, no tracking.

Features

  • 8 Unit Categories — Length, weight, temperature, speed, data, time, area and volume — metric, US and UK units.
  • Type in Either Box — Type in either box and the other one follows; ⇅ swaps the units.
  • Real-Time Results — See conversion results as you type — no button press needed.
  • Exact Definitions — Every factor is the legal definition (1 in = 2.54 cm, 1 lb = 0.45359237 kg, 1 US gallon = 3.785411784 L), so 1 gallon is exactly 128 fl oz, not 128.0000676.

How It Works

  1. Select a category — Choose length, weight, temperature, speed, data, time, area or volume.
  2. Enter a value — Type a number in either box and pick the two units.
  3. Read the result — The other box updates as you type; the line below shows the conversion factor.

Use Cases

  • Convert between metric and imperial units
  • Convert data sizes (KB, MB, GB, TB)
  • Convert Celsius, Fahrenheit, and Kelvin temperatures

Frequently Asked Questions

How accurate are the conversions?

Each unit is converted with its exact definition (1 inch = 2.54 cm, 1 pound = 0.45359237 kg, 1 US gallon = 231 cubic inches = 3.785411784 L, 1 knot = 1852 m per hour) in 64-bit floating point. Results are shown to 12 significant digits, and whole numbers in full — 1 PiB is 1125899906842624 bytes. Month (30 days) and year (365 days) are fixed lengths, not calendar months or years.

What temperature formulas are used?

Standard conversion formulas: F = C * 9/5 + 32, K = C + 273.15, and their inverses.

US or UK gallons, pints and fluid ounces?

Both, each labelled. The US units (teaspoon, tablespoon, fluid ounce, cup, pint, gallon) come from the 3.785411784 L US gallon; the UK imperial pint, fluid ounce and gallon from the 4.54609 L imperial gallon. They differ: a UK pint is 568 mL, a US pint 473 mL, and a UK fluid ounce (28.4 mL) is smaller than a US one (29.6 mL).

Is 1 KB 1000 or 1024 bytes?

Both meanings are in use, so both are here under their own names. KB, MB, GB, TB and PB are decimal: 1 KB = 1000 bytes, the SI meaning used by storage makers and macOS. KiB, MiB, GiB, TiB and PiB are binary: 1 KiB = 1024 bytes. Windows counts in binary but labels the result KB/MB/GB, so to match a size Windows shows you, pick KiB, MiB or GiB.

Notes from Milo 🐨

2026-10-04

Doubling a recipe, I asked this page how many tablespoons are in a cup and it said 15.9999459. A gallon was 128.0000676 fluid ounces, a knot 1.8519984 km/h. The units were right, but I had typed their sizes in rounded to six digits. Every factor is now the exact definition (a US gallon is 231 cubic inches, everything else in the kitchen comes from it), so a cup is 16 tablespoons again. Results show 12 digits and whole numbers in full: 1 PiB is 1125899906842624 bytes, not 1.1259e+15. You can now type in either box, UK pints, gallons and fluid ounces are in the list next to the US ones (they're bigger), anything below absolute zero gets a polite warning, and on a phone the unit menus no longer run off the edge.

2026-10-02

I converted 1 TB here and got 1024 GB, while the box my drive came in says 1000. The reason: this page quietly used 1024 for every KB, MB and GB, which is the Windows way of counting, while drive makers and macOS count in thousands. Both are in use, so now both are here under their own names: KB, MB, GB, TB are thousands, and KiB, MiB, GiB, TiB are 1024s. A short note under the converter explains which is which — including why a 1 TB drive shows up in Windows as about 931 GB (it's 931 GiB).

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💬 Bug, idea, or just to say hi? Tell Milo 🐨 · [email protected]