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Unit Converter
Convert between different units of measurement including length, weight, temperature, volume, and more.
The Unit Converter is your go-to tool for converting between different measurement systems. Whether you're working on math homework, following an international recipe, understanding product specifications, or traveling abroad, this tool handles conversions across multiple categories: length (miles to kilometers), weight (pounds to kilograms), temperature (Fahrenheit to Celsius), volume (gallons to liters), and more. Get instant, accurate conversions without memorizing complex formulas.
Five categories, one box to type in
The row of tabs at the top picks what you are converting: Length, Weight, Temperature, Volume or Area. Choosing a tab reloads both dropdowns with only the units that belong to it, so you are never offered kilograms when you meant kilometres.
Pick a unit on the left, a unit on the right, type a number, and the answer appears straight away in the teal box. There is no convert button and nothing to submit. Underneath, the tool spells the whole thing out as a sentence, so 30 Centimeters = 11.811024 Inches, which is the bit worth copying into homework or a note to yourself.
The round arrows button between the two sides swaps them. It carries the answer across as the new starting value, so if you have just worked out that 5 feet is 1.524 metres, one tap turns it into 1.524 metres back to feet. Handy when you realise halfway through that you had the direction the wrong way round.
What each category covers
Length gives you metres, kilometres, centimetres, millimetres, miles, yards, feet and inches, which covers almost everything people look up: cm to inches, mm to inches, inches to feet, km to miles, meters to feet and the same pairs in reverse.
Weight has kilograms, grams, milligrams, pounds, ounces and metric tons, so kg to lbs, lbs to kg, grams to ounces and mg to g are all a couple of clicks apart. Temperature covers Celsius, Fahrenheit and Kelvin, which is the Fahrenheit to Celsius conversion most people arrive looking for, plus Kelvin for secondary school science.
Volume is US measure: litres, millilitres, gallons, quarts, pints, cups and fluid ounces, useful for liters to gallons and for American recipes that assume you own a set of cup measures. Area has square metres, square kilometres, square feet, square yards, acres and hectares, which is the set you want for a garden plan, a classroom floor or a field.
How the numbers are worked out
Every conversion goes through a base unit rather than a big table of pairs. Length converts through metres, weight through kilograms, volume through litres, area through square metres and temperature through Celsius. That means every combination inside a category works, including the awkward ones like millimetres to yards or ounces to metric tons, and they all use the same exact factors: 0.0254 metres to the inch, 0.453592 kilograms to the pound, 1609.344 metres to the mile.
Temperature is the exception worth knowing about, because it is a scale with an offset rather than a simple multiplier. Fahrenheit comes back as Celsius through subtract 32, multiply by 5, divide by 9, and Kelvin is Celsius plus 273.15. That is why 0 degrees does not mean the same thing in all three.
Results are shown to eight significant figures and then trimmed, so small numbers do not collapse to zero and large ones do not run off the screen. If you want a rounder answer for a worksheet, round it yourself: 2.54 centimetres to the inch is precise, but 1 inch is about 2.5 cm is usually enough for a Year 5 measuring task.
Where it gets used at home and in class
Metric and imperial measurement conversion turns up in the maths curriculum from around age eight, and the questions are almost always the same handful: centimetres to metres, grams to kilograms, millilitres to litres. Working through a few on screen first makes the paper practice go faster, because children can see the decimal point move rather than being told it does.
Outside lessons, it is the kitchen and the shopping list. Recipes written in cups and fluid ounces against a kitchen scale in grams, a height given in feet and inches when the form wants centimetres, an oven set in Fahrenheit when the recipe says 180C. Travel adds miles to kilometres and the daily forecast in the other temperature scale.
It runs entirely in the browser with no account and no sign-in, and it works the same on a phone, a tablet or a classroom desktop. Nothing you type is sent anywhere.
Frequently Asked Questions
How many cm in an inch?
Exactly 2.54 centimetres. Going the other way, one centimetre is about 0.3937 inches, so a quick mental check is that 10 cm is just under 4 inches.
How do I convert kg to lbs?
Choose the Weight tab, set the left dropdown to Kilograms and the right one to Pounds, then type your number. One kilogram is about 2.2046 pounds, so doubling and adding a tenth gets you close in your head.
What is the formula for Fahrenheit to Celsius?
Subtract 32, then multiply by 5 and divide by 9. So 98.6F becomes 37C. The Temperature tab does it for you, and the same tab handles Celsius to Fahrenheit and Kelvin.
Can it convert mm to inches?
Yes. Millimetres and inches are both in the Length tab, along with centimetres, metres, kilometres, feet, yards and miles. One inch is 25.4 mm.
Are the gallons US or UK?
US. Gallons, quarts, pints, cups and fluid ounces all use US measure, so a gallon is 3.78541 litres and a cup is about 237 ml. UK pints and gallons are larger, so imperial recipes will read slightly off.
Why does it show so many decimal places?
Answers are given to eight significant figures so that very small conversions, like milligrams to kilograms, do not round down to zero. Round the result yourself to whatever the worksheet or recipe needs.
Can I convert between categories, like kg to litres?
No, and no honest converter can. That would need the density of whatever you are measuring. Each tab only converts within itself, so weights stay with weights and volumes with volumes.
Does it work offline or on a phone?
It needs the page to load, but after that every calculation happens in your browser rather than on a server. The layout stacks on a phone screen, so it is fine for looking something up in a shop or a kitchen.