Converters Calculators
Unit, currency & measurement converters. All tools are free, instant, and updated for 2026.
Length Converter
Convert length & distance units
Use calculatorWeight Converter
Convert weight & mass units
Use calculatorTemperature Converter
Convert temperature units
Use calculatorAbout Converters calculators
Unit conversion is one multiplication, so the interesting part is never the arithmetic — it is knowing which unit you actually have. An ounce of gold and an ounce of flour are different masses. A British ton is heavier than an American one. A fluid ounce is not a weight at all.
Every conversion here routes through a single base unit rather than chaining, which is why converting out and back returns exactly the number you started with.
What to watch when converting
- Weight and mass are not the same quantity
- Kilograms measure mass; pounds are conventionally used for both mass and force. Everyday conversion works because gravity is near enough constant on Earth, but the distinction matters the moment physics is involved.
- Temperature scales have offsets, not just factors
- Celsius to Fahrenheit needs both a multiplier and an added constant, which is why you cannot convert a temperature difference the same way you convert a temperature. A 10 degree Celsius rise is an 18 degree Fahrenheit rise, not 50.
- US and imperial units share names but not sizes
- A US gallon is about 3.785 litres; an imperial gallon is about 4.546. Pints and fluid ounces diverge the same way. Recipes and fuel figures crossing the Atlantic go wrong here more often than anywhere else.
- Rounding early compounds through a chain
- Converting in several steps and rounding at each one accumulates error. Convert once, from the original figure to the final unit, and round only at the end.
- Significant figures should survive the conversion
- Converting a measurement good to two digits into one displayed to six does not add information. The extra digits are an artefact of the arithmetic, not knowledge about the thing you measured.
Which one do you need?
- You are converting body weight or shipping mass
- Weight — and check whether an "ounce" is troy or avoirdupois if precious metals are involved.
- You are working with distance or height
- Length, which uses the exact 0.3048 m definition of a foot.
- You are converting temperature
- Temperature, which handles the offset that ratios cannot.
Where these go wrong
Converting a temperature difference like a temperature
The Celsius to Fahrenheit conversion includes an offset. A difference of 10 degrees Celsius is 18 degrees Fahrenheit, not 50.
Mixing US and imperial volumes
A US gallon is about 3.785 litres and an imperial gallon about 4.546. Pints and fluid ounces diverge the same way, which catches recipes and fuel figures constantly.
Rounding at every step of a chain
Each intermediate rounding adds error. Convert once from the original figure and round only at the end.
Assuming a unit name means one thing
Tons, ounces and pints all have more than one definition in current use. Check which system a figure came from before converting it.
Common questions
Why is a troy ounce different from a regular ounce?
They come from different historical systems. Precious metals kept the troy system while ordinary trade moved to avoirdupois. A troy ounce is 31.1035 g against 28.3495 g — about 10% heavier — so confusing them misprices a metals transaction by roughly a tenth.
Can I convert cups to grams?
Not without knowing the ingredient. A cup measures volume and a gram measures mass, so the conversion depends on density. A cup of flour is about 120 g and a cup of sugar about 200 g. This is the most common reason a converted baking recipe fails.
Are these conversions exact?
Where an exact definition exists, yes — a pound is exactly 0.45359237 kg and a foot exactly 0.3048 m, both fixed by international agreement. Rounded factors introduce small errors that compound if you chain conversions, which is why everything here goes through one base unit.
Why does my conversion differ slightly from another tool?
Usually rounding, occasionally definitions. Some conversions are exact by definition, such as an inch being 25.4 millimetres, while others are derived and get rounded at different points. Differences in the last digit or two are almost always this and not an error.
Which gallon or ton am I using?
US customary unless stated otherwise. It matters: the US and imperial gallon differ by about twenty percent, and short, long and metric tons are three different masses that share a name.
Can I convert between mass and volume?
Only if you know the density of the substance. Grams and millilitres coincide for water at room temperature and for nothing else reliably, which is why flour and sugar measured by volume vary so much between kitchens.
Are these conversions exact?
Where the relationship is defined, yes, and the display rounds only for readability. Where it is derived from a measured constant, the result carries that constant's precision, which is far beyond anything ordinary use requires.