Unit Converter

About the Unit Converter

The Unit Converter instantly converts length, weight, temperature, volume, data, speed, and more — and shows every related unit at once, so you can compare values across the whole measurement system in a single view.

The conversions people actually get wrong

• Square feet to square metres. One square metre is 10.7639 square feet — the factor is nearly eleven, not three, and estimating in your head goes badly wrong. A "1,200 sq ft" flat is about 111.5 m². This one matters because price per square metre is one of the few objective ways to compare two properties, and it collapses if the area is 8% out.
• Recipes across the Atlantic. US cups are a volume measure and European recipes weigh, so the answer depends on the ingredient. Convert what converts cleanly — temperatures, millilitres, grams and ounces — and be suspicious of anything that claims a single cups-to-grams number for flour.
• Oven temperatures. Fahrenheit to Celsius needs an offset as well as a scale factor, which is why halving numbers doesn't work and why gas marks catch people out.
• Data sizes. Drive manufacturers count a gigabyte as 1,000,000,000 bytes while your operating system often counts 1,073,741,824. That gap is the entire explanation for why a "1TB" drive shows up as 931GB.
• Fuel economy, where miles per gallon and litres per 100km run in opposite directions — a bigger number is better in one and worse in the other.

Why the numbers here are exact

Where an exact definition exists, this converter uses it rather than a rounded approximation. An inch is defined as precisely 25.4 millimetres; a pound is exactly 0.45359237 kilograms. Everything converts through a single base unit per category rather than chaining conversions together, because chaining is where rounding error accumulates — convert feet to metres to centimetres to inches through three roundings and you can come back with a different number than you started with.

Converting to every unit in a category at once is deliberate. It's usually faster to scan a full column than to pick a target unit, and it catches the case where you were converting to the wrong one.

Works well with

Property listings are the most common reason people land here, and the Mortgage Calculator is usually the next stop. The buying a home guide covers both together, including the acre-and-hectare conversions that appear the moment a listing mentions land.

Frequently Asked Questions