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Unit Converters

Length, weight, temperature, volume and more — converted with exact defined factors and full tables.

Unit Converter⇄Convert between metric and imperial units across length, weight, temperature, volume and more — with exact defined factors, in your browser.Open tool →Length Converter⇄Convert metres, feet, inches, miles and kilometres with exact defined factors and a full reference table — instantly, in your browser.Open tool →Weight & Mass Converter⇄Convert kilograms, pounds, stone, ounces and tonnes with exact factors — including the stone conversion UK scales actually use, in your browser.Open tool →Temperature Converter⇄Convert Celsius, Fahrenheit and Kelvin with the exact formulas and a reference-points table — no offset mistakes, in your browser.Open tool →Volume Converter⇄Convert litres, gallons, cups and fluid ounces with US and imperial gallons kept separate — exact factors and tables, in your browser.Open tool →Area Converter⇄Convert square metres, square feet, acres and hectares with exact defined factors and a full unit table — instantly, in your browser.Open tool →Speed Converter⇄Convert miles per hour, kilometres per hour, knots and metres per second with exact factors and reference speeds, in your browser.Open tool →Pressure Converter⇄Convert pascals, bar, psi and atmospheres with exact defined factors and typical values for tyres and weather, in your browser.Open tool →Energy Converter⇄Convert joules, calories, kilowatt-hours and BTU with exact defined factors and everyday reference amounts, in your browser.Open tool →Data Storage Converter⇄Convert bytes, kilobytes, megabytes and gigabytes — decimal and binary units kept separate and explained, in your browser.Open tool →Cooking Converter⇄Convert cups to grams and back by ingredient, using published reference weights for flour, sugar, butter and more, in your browser.Open tool →Fuel Consumption Converter⇄Convert MPG to litres per 100 km and back for US and imperial gallons — the inverse conversion explained, in your browser.Open tool →Roman Numeral Converter⇄Convert Roman numerals to numbers and numbers to Roman numerals up to 3,999, with the subtractive rules explained, in your browser.Open tool →

About these unit converters

Every converter in this category is built on defined factors, not measured approximations. The inch is exactly 2.54 centimetres, the foot exactly 0.3048 metres, the pound exactly 0.45359237 kilograms and the US gallon exactly 3.785411784 litres, fixed by international definition. That matters because a conversion is only as trustworthy as its factor: use 2.5 cm for an inch and a long length is already out by more than a centimetre before rounding even starts. Each page prints the factor and formula it uses, works through real examples with the substitution shown, and keeps full precision internally, rounding only the number it displays.

The all-in-one Unit Converter covers breadth, ten or more quantity types on one page, while the category converters cover depth: length, weight, temperature, volume, area, speed, pressure, energy, data storage, cooking and fuel consumption each get a full unit grid, a reference table and the traps that belong to that quantity. Temperature is the reminder that not everything is a simple multiplication, because its scales have different zeros as well as different steps. Fuel consumption goes further and inverts: a higher miles-per-gallon figure is better, a higher litres-per-100-km figure is worse, and converting between them means dividing a constant, not multiplying by one.

Three traps run through the whole category and are named wherever they apply. First, names collide across the Atlantic: a US gallon is about 20 percent smaller than an imperial gallon, a US ton is not a metric tonne, and a US cup is not a metric cup. Second, similar-looking units hide different systems, most clearly in data storage, where a megabyte of 1,000,000 bytes and a mebibyte of 1,048,576 bytes are both in live use and explain why a drive can appear smaller than its box promised. Third, everyday units survive that general converters fumble, such as the stone of exactly 14 pounds in British body weight. Read the method section on any page before trusting a figure you will act on, and use batch mode when a whole list needs converting at once.

Frequently asked questions

Are the conversion factors used here exact?

Yes, for the units defined by international agreement. The inch, foot, mile, pound, US gallon and imperial gallon all have exact metric definitions, which are printed on each converter page alongside its formula. A small number of reference values, such as the speed of sound or a battery's stored energy, are labelled as approximate wherever they appear, and are never used as conversion factors.

Why is one answer from a search widget sometimes not enough?

A widget converts one value into one unit and stops. Real tasks usually need more: a full table to read neighbouring values from, a list of measurements converted together in batch mode, a result expressed as feet and inches rather than decimal feet, or a check on which gallon, ton or cup a source meant. The category pages carry the tables, batch mode and named traps that a single answer cannot.

Do these converters store what I enter?

No. Every converter on Kwikfig runs entirely in your browser. The values you type or paste for batch conversion are never sent to a server, stored or tracked — close the tab and they are gone.