Overview

Most conversions start as a sentence in your head: how tall is 5 ft 11 in in centimetres, what is 180 °C on a gas oven, how many grams is a cup of atta, how many acres is a bigha. ConvertAll lets you type that sentence as it is and gives the answer, with the formula and a note on whether it is exact.

Behind the search bar sit 33 categories with over 370 units, from length, weight and volume to pressure, energy, electricity and radiation, each with a yellow tape that shows both scales at once and a list of the value in every unit. Around them are practical tools for the kitchen, sizes, travel, numbers and health, and Indian units such as the tola, the bigha and lakh and crore sit beside the metric and US ones.

All of it runs in your browser: what you type stays on your device.

Key Features

How to Use

1. Type a conversion - In the search bar type something like 30 psi in bar and press Enter, or pick a category from the list.
2. Change either side - Type in the From or the To box; the other follows. Fractions, sums and mixed units such as 5 ft 11 in work in both.
3. Read the answer - The line under the boxes gives the result, the formula and a tag: Exact, Rounded or Approximate.
4. Look around the value - Drag the yellow tape, or read the value in every unit in the list below it.
5. Keep what you use - Save a pair to keep it in the quick pairs row, and find recent conversions under Saved.
6. Open a tool - Cooking, recipes, oven heat, sizes, trip cost, tyres, time zones, number bases, paper, wire gauges, BMI or lakh and crore.

How the Tool Works It Out

• Unit sizes - From the published definitions: NIST Special Publication 811 and NIST Handbook 44 (on the international foot, since the US survey foot was retired at the end of 2022), the SI Brochure, CODATA 2022 for the dalton, the CSS standard for screen units, NIST's binary prefixes, and the Standards of Weights and Measures Act, 1976 for the tola, seer and maund.
• Exact or rounded - An answer is exact when the two units relate by a short decimal and every digit is shown; temperatures add as well as multiply, and fuel economy turns upside down between km per litre and litres per 100 km.
• Kitchen - The weight of a cup of each ingredient is the U.S. Department of Agriculture's (FoodData Central); gas marks and fan ovens follow the oven chart of Which?, the UK consumer body.
• Trip and health - CO₂ from the US EPA's figures for a gallon of petrol and diesel; BMI with the WHO's cut-offs or the India Obesity Commission's of 2025.
• Charts - Clothing, shoe and ring sizes are example charts, because brands size differently; land units such as the bigha are named with the size each uses, because they differ by place.
• Checked before publishing - We compared the tool with references made separately: 101,252 cases in 13 groups: every unit's size worked out again from its published definition and compared with NIST's tables, conversions between every pair of units in each category against a separate calculation, typed values read back in all five number formats, the smart search, the recipe scaler, the tyre code, number bases and amounts in words each against a reference written from their rules, 3,003 saved states made to break it, and long input that kept the original busy for more than 20 seconds, now answered in milliseconds. When UnitSwap was merged in on 15 November 2026, the 24 added units, and everything the tool read and converted before, were checked again on 64,322 cases.

Conversions in Everyday Life

In the kitchen, weigh when you can. A cup of all-purpose flour is 125 g by USDA's figure, but flour scooped and pressed into the cup weighs more than flour spooned in; the cooking tool gives the weight, and Other takes the figure from your own scale. For an oven, remember that a fan oven runs hotter: the recipe's 180 °C is about 160 °C with a fan.

For land, ask which bigha. The same word can mean 27,225 square feet in one district and 14,400 in another, so ConvertAll names each size; check the one in your land records before you rely on a figure. For gold, a tola is 11.6638038 g (180 grains), the size the Standards of Weights and Measures Act, 1976 gives.

ConvertAll puts many conversions in one place, and since 15 November 2026 it is the site's one unit converter: UnitSwap, the earlier one, became part of it. A few of its tools are also tools of their own on this site: BaseShift converts number bases, the Time Zone Converter compares cities, AutoCalc goes deeper into tyre sizes and trip costs, HomeCalc measures property areas with land units, EngCalc sizes cables, and Passport Photo Maker makes passport photos.

Eight Temperature Scales

Temperature is the one everyday measure where a conversion is not a single multiplication, because the scales start at different points. ConvertAll converts between eight of them. Most are fixed by two points, where water freezes and where it boils:

• Celsius - water freezes at 0 and boils at 100.
• Fahrenheit - 32 and 212, so °F = °C × 9/5 + 32.
• Kelvin - degrees the size of Celsius ones, counted from absolute zero: K = °C + 273.15.
• Rankine - degrees the size of Fahrenheit ones, counted from absolute zero: °R = °F + 459.67.
• Réaumur - 0 and 80, so one Réaumur degree is 1.25 Celsius degrees.
• Delisle - it runs the other way: 0 where water boils and 150 where it freezes, so a bigger number is colder. °De = (100 - °C) × 3/2.
• Rømer - 7.5 and 60, so °Rø = °C × 21/40 + 7.5.
• Newton - 0 where water freezes and about 33 where it boils. The scale was never fixed by a second point, so ConvertAll marks it Approximate.

Celsius and Fahrenheit show the same number at one temperature only. Put the same number on both sides of °F = °C × 9/5 + 32 and it works out to -40, so -40 °C is -40 °F. Nothing can be colder than absolute zero (0 K, which is -273.15 °C), so ConvertAll tells you when a value you typed lies below it.

Fuel Economy Runs Both Ways

Fuel economy is written in two ways. Kilometres per litre and miles per gallon say how far a vehicle goes on a measure of fuel, so a bigger number is better. Litres per 100 km says how much fuel a set distance takes, so a smaller number is better. To go from one kind to the other you divide instead of multiplying: 20 km per litre is 5 litres per 100 km, and 10 km per litre is 10. A US gallon is also smaller than a UK gallon, so 30 miles per US gallon is about 36 miles per UK gallon; ConvertAll keeps the two apart.

This is why equal steps in miles per gallon do not save equal amounts of fuel. Over 10,000 miles a car that does 10 mpg burns 1,000 gallons and one that does 20 mpg burns 500, a saving of 500 gallons. Going from 30 to 50 mpg saves only about 133 gallons (333 against 200). Litres per 100 km shows this directly, because it rises and falls with the fuel used.

A Few Unusual Units

Among the units are some you rarely meet. Most of these came over from UnitSwap:

• Barn - a unit of area from nuclear physics for the size of the target an atomic nucleus presents to a particle. It takes 10²⁸ barns (1 followed by 28 zeros) to make a square metre.
• Shake - 10 nanoseconds, an informal unit of time that also comes from nuclear physics.
• Slug - the mass that a force of one pound speeds up by one foot per second every second: about 32.174 pounds, or 14.594 kg.
• Poundal - the force that speeds up a mass of one pound by one foot per second every second, about 0.138 newton.
• Square rod and rood - old land measures. A square rod is 272.25 square feet, 40 of them make a rood, and four roods make an acre.
• Quadrant, sextant and sign - a quarter, a sixth and a twelfth of a full turn: 90, 60 and 30 degrees.
• Boiler horsepower - 9,809.5 watts, about thirteen times a mechanical horsepower.

Three of UnitSwap's units were not brought over, because they have no single fixed size: Mach (the speed of sound changes with the air), the jiffy (it stands for several different lengths of time) and the computer word (its size depends on the kind of computer).

Frequently Asked Questions

The questions people ask most are answered on the tool page, just below the tool. The full list of 32 questions, from typing a conversion to the sources of the figures, Indian units, kitchen, sizes and BMI, is on the ConvertAll FAQ page, and every part of the tool is explained step by step in the help guide.

Privacy & Security

The tool asks no outside service for anything. Like every page on ZeroDataUpload, the tool page shows ads through Google AdSense and counts visits with Google Analytics; the Privacy Policy explains both.

Related

Last Updated: November 15, 2026