Unit Converter

Related guide

Unit and Base Converters: Factors, Display Rounding and the Edges of the Range
The unit converter multiplies by one stored factor per unit; the base converter re-encodes an integer exactly. Both are reliable in the middle and surprising at the edges — exactly 1,000,000 switches to scientific notation, 1 PB comes out as 1023.999994 TB, and the box you type in keeps the leading zeros you gave it. Every figure below was measured on the pages themselves.

What it covers

Eight categories — length, weight, temperature, area, volume, speed, time and data storage — with about seventy units in total, including the units used in Chinese-speaking regions alongside the metric and imperial ones: li, zhang, chi and cun for length; jin, liang and qian for weight; and mu and fen for area.

Pick a category, choose the units on each side, and the result updates as you type. The arrow button swaps the two units, and the line underneath shows the conversion in the form "1 kilometre = 0.621371 mile" so you can see the factor being applied.

How the conversion is done

Every unit is stored as a factor to its category's base unit — metre, kilogram, second, byte, and so on. Converting is then value × from-factor ÷ to-factor, which is why results are consistent no matter which direction you convert in.

Temperature is the one exception: degrees cannot be scaled with a single factor because the scales have different zero points, so those conversions go through Celsius with the standard formulas ((°F − 32) × 5/9 and °C + 273.15).

How much precision you get

Values between 0.001 and 1,000,000 are shown with up to six decimal places and trailing zeros removed. Outside that range the display switches to scientific notation with four decimals, and anything smaller than 1e-10 is shown as 0. The rounding is in the display only — the underlying factors are not rounded.

The factors themselves are the defined values where they exist: an inch is exactly 0.0254 m and a pound is exactly 0.45359237 kg by definition. For long conversions, convert once rather than in several steps so rounding cannot accumulate.

Conventions worth knowing

Data storage uses binary multipliers: 1 KB is 1024 bytes, 1 MB is 1024 KB, and so on. Storage vendors tend to use 1000-based units, which is why a "1 TB" drive reports around 931 GB in your operating system.

A year here is 365 days and a month is 30 days, so time conversions are averages rather than calendar-exact. Speed of sound is taken as 343 m/s — the value at 20 °C at sea level. Gallons, quarts, pints and fluid ounces are the US liquid measures.

FAQ

How do I convert Fahrenheit to Celsius?
Choose the temperature category, put the value in the Fahrenheit box and set the other side to Celsius. The formula applied is (°F − 32) × 5/9, so 98.6 °F is 37 °C. Kelvin is handled the same way, through absolute zero: K = °C + 273.15.

Is 1 GB 1000 MB or 1024 MB?
This converter uses 1024, the binary convention that operating systems report in. Drive manufacturers use powers of 1000, so a disk sold as 1 TB shows as roughly 931 GB in Windows or macOS. Both numbers are correct in their own convention — the confusion is in the naming, not the arithmetic.

Why did the result change to something like 1.2345e+7?
That is scientific notation: 1.2345 × 10⁷. It appears when the result falls outside the 0.001 to 1,000,000 window, where fixed-point notation would either lose detail or become hard to read. Convert to a smaller unit if you prefer plain digits.

How accurate are the conversions?
The factors are exact where the units are defined in terms of each other — an inch is 0.0254 m and a pound is 0.45359237 kg by definition, not by measurement. Average-based units such as the month (30 days) and the speed of sound (343 m/s at 20 °C) are the ones to check if your application needs a specific standard.

Which ton and which gallon does it use?
The ton here is the metric tonne (1000 kg) and the gallon is the US liquid gallon (3.785412 litres). The US short ton (907.18 kg), the UK long ton (1016.05 kg) and the imperial gallon (4.54609 litres) are not in the list.

Can I convert millilitres to grams?
Not directly — that is a volume-to-mass conversion and it depends on the density of the substance, about 1 g/mL for water but very different for oil, honey or flour. Convert within a category, or use a density figure to bridge the two.