Convert Length, Weight, Temperature, Area and Volume units in real time. 50+ units supported β instant live conversion as you type. Free, private and browser-based.
The need to measure and convert units is as old as human civilisation itself. Ancient Egyptians measured length using the "cubit" β the distance from the elbow to the tip of the middle finger β while the Romans used "mille passuum" (a thousand paces, from which we get the word "mile"). The ancient Indian system used units like "angul" (finger width) and "hasta" (hand span). The problem with all of these early systems was obvious: a cubit varied from person to person, a pace from soldier to soldier. Commerce, construction and science demanded something more consistent.
The French Revolution of the 1790s brought a dramatic solution: the metric system. French scientists proposed a universal, decimal-based system rooted in nature β the metre was defined as one ten-millionth of the distance from the Earth's equator to the North Pole along a meridian. This system, refined over two centuries into today's International System of Units (SI), is now used by virtually every country in the world for science, medicine and most commercial activities.
Yet the imperial system β with its inches, feet, miles, pounds and gallons β persists strongly in everyday use in the United States, and partially in the United Kingdom, India and other countries for certain applications. This coexistence of two major measurement systems is why unit conversion tools are needed daily by engineers, students, travellers, cooks, builders and anyone working across international contexts. Our All-in-One Unit Converter Pro handles all of these conversions instantly and accurately.
Length is the most commonly converted unit type. Whether you are reading US product dimensions, following a European recipe, planning a road trip or studying physics, knowing how to convert between different length units is an essential everyday skill.
| Unit | Equivalent in Metres | Common Use |
|---|---|---|
| Millimetre (mm) | 0.001 m | Engineering, jewellery, screen specs |
| Centimetre (cm) | 0.01 m | Height, clothing, everyday measurement |
| Metre (m) | 1.000 m | SI base unit β rooms, fabric, athletics |
| Kilometre (km) | 1,000 m | Road distances, geography |
| Inch (in) | 0.0254 m | Screen sizes, US construction |
| Foot (ft) | 0.3048 m | Height (US/UK), altitude, real estate |
| Yard (yd) | 0.9144 m | American football, fabric |
| Mile (mi) | 1,609.34 m | Road distances (US/UK) |
| Nautical Mile | 1,852 m | Aviation and maritime navigation |
π Most searched conversions: 1 inch = 2.54 cm | 1 foot = 30.48 cm | 1 mile = 1.609 km | 1 km = 0.621 miles | 5 feet 7 inches = 170.18 cm
Weight conversion is essential for international shipping, cooking, medicine, fitness and science. The distinction between weight (a force caused by gravity) and mass (an inherent property of matter) is important in physics, but in everyday usage the terms are used interchangeably and both refer to how heavy something is.
The kilogram is the SI base unit of mass and is defined with extraordinary precision β since 2019 it has been defined by fixing the Planck constant to exactly 6.62607015 Γ 10β»Β³β΄ joule-seconds, making it one of the most precisely defined units in human history. At the other end of the scale, the metric tonne (1,000 kg) is used for heavy goods, vehicles and cargo, while the milligram is essential in pharmacy and chemistry.
The imperial system uses ounces (oz), pounds (lbs) and stone (st, used in the UK for body weight) β none of which divide evenly into each other in a logical decimal fashion. There are 16 ounces in a pound, 14 pounds in a stone and 2,240 pounds in a long ton. Our converter handles all of these relationships automatically so you never need to remember the conversion factors.
Temperature conversion is unique among unit conversions because it involves both multiplication and addition β unlike length or weight conversions which only require multiplication by a fixed factor. This is because the three major temperature scales (Celsius, Fahrenheit and Kelvin) have different zero points.
| Scale | Water Freezes | Water Boils | Absolute Zero | Used In |
|---|---|---|---|---|
| Celsius (Β°C) | 0Β°C | 100Β°C | -273.15Β°C | Most of the world |
| Fahrenheit (Β°F) | 32Β°F | 212Β°F | -459.67Β°F | USA, some Caribbean nations |
| Kelvin (K) | 273.15 K | 373.15 K | 0 K | Science & physics worldwide |
The key formulas: Β°F = (Β°C Γ 9/5) + 32 and Β°C = (Β°F β 32) Γ 5/9. Kelvin is simply Celsius shifted by 273.15 β K = Β°C + 273.15. Kelvin is used in physics because it starts at absolute zero (the coldest possible temperature, where all molecular motion stops), making calculations involving thermodynamic laws cleaner and more intuitive.
Area conversions are critical for real estate, agriculture, construction and land measurement. In India, traditional area units like bigha, gunta, cent and ground are still widely used alongside the modern metric units of square metres and hectares. One hectare equals 10,000 square metres β approximately the size of a standard sports pitch. One acre equals 4,047 square metres and is the dominant land measurement unit in the United States, United Kingdom and much of South Asia for agricultural land.
Volume conversion is essential for cooking, chemistry, medicine and fuel measurement. The litre is the most commonly used volume unit worldwide, while the US uses fluid ounces, cups, pints, quarts and gallons for cooking β all of which differ from their UK equivalents (a US gallon is 3.785 litres while a UK gallon is 4.546 litres). In medicine and pharmacy, millilitres (mL) and cubic centimetres (cc, which are numerically equal to mL) are the standard units. Our converter supports all major volume units including the US and UK variants.
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