Converters Calculators
Units, bases and data sizes
One tool for many units, or one page per pair
There are two ways to convert something, and they suit different moments. The unit converter handles every category at once — length, weight, volume, area, speed, temperature, data and more — which is what you want when you are working through a problem and the units keep changing. The dedicated conversion pages do exactly one pair each, with the factor, the formula, a worked example and a reference table, which is what you want when you have a single number and want it converted and explained.
Temperature is the exception that shapes the whole category. Celsius, Fahrenheit and Kelvin have different zero points as well as different degree sizes, so converting between them needs an offset as well as a multiplication — which is why a temperature conversion can never be expressed as a simple factor, and why the temperature converter shows all three scales together rather than two at a time.
Cooking, where volume is not weight
Kitchen conversion is the one place where a straight unit conversion gives the wrong answer. A cup is a volume; a gram is a mass; and a cup of flour, a cup of sugar and a cup of honey weigh dramatically different amounts. Converting between them requires the density of the specific ingredient, which is why the cups to grams converter asks what you are measuring rather than applying one factor to everything.
The cooking converter handles the rest of the kitchen — cups, spoons, millilitres and grams — with the same ingredient awareness. It also carries the regional trap worth knowing about: a US customary cup is 236.6 ml, a metric cup is 250 ml and an old imperial cup was 284 ml, so a recipe that crosses a border rarely survives the trip unadjusted.
Converters calculators — common questions
Should I use the full unit converter or a single-pair page?
Use a single-pair page when you want the answer explained — it carries the exact factor, the formula both ways, a worked example and a table of common values you can scan. Use the full unit converter when you are moving between many units, or when the pair you need does not have a page of its own.
Why does my hard drive show less space than advertised?
Because two different definitions of a gigabyte are in play. Drive manufacturers use the decimal one, 10⁹ bytes; most operating systems report in binary, 2³⁰ bytes, which is about 7% larger. A 1 TB drive is therefore around 931 GiB of reported space, and nothing is missing. The data storage converter shows both columns side by side so the gap is visible rather than mysterious.
Is a US gallon the same as an imperial gallon?
No, and the gap is large. A US gallon is 3.785 litres; an imperial gallon is 4.546 litres, about 20% bigger. This is why UK fuel economy figures in miles per gallon look better than American ones for the same car. Separate pages cover each, and mixing them up is one of the more expensive conversion mistakes available.
How precise are the conversions?
The factors are the exact defined values where one exists — an inch is exactly 25.4 mm, a pound is exactly 0.45359237 kg — and full double precision throughout. Results are rounded for display only, so what you read is a rounded view of an exact calculation rather than a calculation done on rounded numbers.