/01 One converter for every measurement
A unit converter answers the questions that interrupt everything: how many kilometres in ten miles, what 180 degrees Celsius is in Fahrenheit, how many millilitres in a US cup. Rather than searching each one, you type the value once and read the answer, across seven categories of measurement.
The categories cover the everyday range: length, weight, temperature, data, speed, area, and volume. Each one lists its units side by side, so you pick what you have and what you want, and the result updates as you type. A metre in miles, feet, and inches at once. A kilogram in pounds, ounces, and stone.
The situations add up quickly. Cooking from a recipe written for another country. Reading an engineering spec that mixes metric and imperial. Checking whether luggage is over the weight limit. Working out running pace. Converting a download speed from megabits to megabytes. Every one of them is a one-liner here.
/02 Temperature: the odd one out
Temperature is the category that catches people, because it is the one where the conversion is not a simple multiplication. Length never changes its zero point: zero inches and zero centimetres are the same amount of nothing, so converting is just a scale factor. Temperature scales disagree about where zero sits. Celsius puts it at water's freezing point, Fahrenheit puts it 32 degrees below that, and the two scales also disagree about the size of a degree.
So converting an actual temperature takes a shift and a scale: subtract 32, then multiply by five ninths, going from Fahrenheit to Celsius. That is why a pleasant 75 degrees Fahrenheit is a mild 24 in Celsius, and why body temperature of 37 Celsius is a worrying-looking 98.6 Fahrenheit that is actually fine.
The trap to know about: a change in temperature converts differently from a temperature. A rise of 10 degrees Celsius is a rise of 18 degrees Fahrenheit, not a rise of 50. The shift only applies when you are standing at a real temperature, not measuring a gap between two.
/03 US and imperial units with the same names
The metric system is consistent everywhere. The traditional systems are not. The US and the UK both use gallons, pints, and fluid ounces, and they mean different amounts by all three. A US gallon is about 3.79 litres. An imperial gallon, the British one, is about 4.55, a fifth larger. The pints differ the same way, which is why an American pint of beer and a British pint are different drinks, and why a UK recipe halved for US measuring cups can come out wrong.
This converter lists both. Gallon US and Gallon UK are separate entries, and the pint, quart, and fluid ounce entries follow the US convention, which is what most recipes online mean when they say a cup or a pint.
The habit to build: when a measurement is in traditional units and the source does not say which system, check where it came from. An American recipe means US volumes. A British one means imperial. The gap between them is large enough to matter in cooking and more than enough in anything technical.
/04 Data units and the drive space puzzle
The data category answers one of the most asked questions in computing: why does a new drive show less space than the box promised? The answer is that two counting systems share the same words. To a manufacturer, a kilobyte is 1,000 bytes: kilo means thousand, and they are counting in thousands. To an operating system, a kilobyte has traditionally meant 1,024 bytes, because computers address memory in powers of two, and 1,024 is two to the power of ten.
The gap compounds as the numbers grow. At a kilobyte it is a 2.4 percent difference. At a terabyte it is nearly 10 percent, which is why a drive sold as 1TB shows up as roughly 931GB. Nothing is missing. The two sides are counting differently and neither is wrong.
The converter gives you the honest picture, and the same category covers bits, kilobits, megabits, and gigabits, the units internet speeds are sold in. Since there are eight bits in a byte, a 100 megabit connection moves at most 12.5 megabytes per second, and that arithmetic is worth having a converter do for you rather than trusting mental maths in the moment.
/05 An online unit converter that shows every unit at once
A search engine's built-in converter answers one pair of units at a time. This unit converter answers the whole row: type a value once and see it in every unit in that category together, which is quicker when you are not sure which unit you need yet. Enter 5 kilometres and read miles, feet, yards and metres in one glance.
It is a web page, not an app, so it opens in any phone or desktop browser without an install, an account or ads. Once loaded, the conversions happen on your device, which means it keeps working with a weak signal on a building site or in a kitchen.
Know the edges too. The seven categories cover length, weight, temperature, data, speed, area and volume. Power, energy and pressure are not included, and time durations and time zones live in the separate Time Calculator.