Unit Converter

Last updated: October 1, 2026

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What is Unit Converter?

Convert between units across twelve categories — length, weight, temperature, area, volume, speed, time, digital storage, energy, pressure, angle and fuel economy. Enter a value once and it appears in every unit in that category at once, each with its own copy button, rather than making you pick a single target and convert again for the next one.

Why seeing every unit at once helps

Most converters ask for a from-unit and a to-unit and give you one number. That is fine when you know exactly what you want, and annoying the rest of the time — when you are reading a recipe in cups and thinking in millilitres and grams, or checking whether a 15-inch laptop fits a 40-centimetre bag, or working out what a 65-inch television is in metres.

Here you type the value and read off whichever line you need, with the unit you entered highlighted so you can see where you started. Each row has a Copy button, so the number goes straight to your clipboard at full precision.

The gallon trap

US and UK gallons are not the same, and confusing them is the single most common unit mistake in everyday use. A US gallon is about 3.79 litres, a UK gallon about 4.55 — roughly 20% larger. American recipes, fuel figures and container sizes use the US gallon; older British figures use the imperial one.

Both are listed separately here, as US gal and UK gal, so you do not have to guess which one a converter means. Pints, quarts and fluid ounces differ between the two systems for the same reason.

Why your hard drive looks smaller than the box said

Digital storage has two competing definitions. This converter uses the binary one, where a kilobyte is 1,024 bytes, a megabyte is 1,024 kilobytes and so on — which is how Windows reports file and drive sizes.

Drive manufacturers use the decimal definition instead, where a gigabyte is exactly 1,000,000,000 bytes. That is why a "500GB" drive shows as about 465GB once plugged in: nothing is missing, the two sides are counting differently, and the gap widens as the numbers get larger.

Fuel economy runs backwards

Miles per gallon and litres per 100 kilometres measure the same thing in opposite directions. With mpg, higher is better — more distance per unit of fuel. With L/100km, lower is better — less fuel for the same distance. They are not proportional, so you cannot convert with a single multiplier, and doubling one does not halve the other.

The converter handles that inversion for you, which matters when comparing a car advertised at 45 mpg against one rated at 6.5 L/100km. And remember the gallon question applies here too: 45 mpg means something different in the US and the UK.

Temperature and the other categories

Temperature converts differently from everything else, because the scales have different zero points as well as different sizes of degree — which is why you cannot simply multiply. Celsius, Fahrenheit, Kelvin and Rankine are all handled. Elsewhere you will find nautical miles and light years under length, stone alongside US and UK tons under weight, knots and Mach under speed, and BTU beside kilowatt-hours under energy.

Everything is calculated in your browser, so nothing is sent anywhere and there is no account or limit.

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How to Use Unit Converter

Select a Category
Choose from 12 categories: Length, Weight, Temperature, Area, Volume, Speed, Time, Digital Storage, Energy, Pressure, Angle, or Fuel Economy.
Enter Value and From Unit
Type your value and select the source unit. Results for all units in the category appear instantly.
Copy Any Result
The results table shows conversions to all units simultaneously. Click Copy next to any row to copy that value.

Features

All Results at Once

See conversions to all units simultaneously in a table - no need to convert one at a time.

Temperature Support

Celsius, Fahrenheit, Kelvin, and Rankine with accurate non-linear conversion formulas.

Live Conversion

Results update instantly as you type - no button click required.

Frequently Asked Questions

What is the difference between a US gallon and a UK gallon?

A US gallon is about 3.79 litres and a UK gallon about 4.55, roughly 20% larger. Both are listed separately here so you never have to guess which one a converter means. Pints, quarts and fluid ounces differ between the two systems too.

Why does my hard drive show less space than advertised?

Two different definitions. This converter and Windows use 1,024 bytes to a kilobyte; drive manufacturers use 1,000. That is why a 500GB drive shows as roughly 465GB. Nothing is missing — the two sides count differently, and the gap grows with size.

How do I convert mpg to L/100km?

They run in opposite directions: higher mpg is better, lower L/100km is better, and they are not proportional, so there is no single multiplier. The converter handles the inversion. Check whether an mpg figure is US or UK as well, since those differ.

Can I see one value in several units at once?

Yes, and that is the main difference here. Enter a value and it is shown in every unit in that category at once, with the unit you entered highlighted and a copy button on each row.

What categories are covered?

Twelve: length, weight, temperature, area, volume, speed, time, digital storage, energy, pressure, angle and fuel economy. Less common units are included too, such as nautical miles, light years, stone, knots, Mach, Rankine and BTU.

Is anything sent to a server?

No. Every conversion is calculated in your browser, so nothing is transmitted and there is no account, no limit and no tracking of what you convert.