Unit converters
Length, weight, volume, temperature, cooking, sizing, and screen measurements.
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Most popular
All units tools
Millimetres to inches, metres to feet, kilometres to miles — every unit at once.
Kilograms, pounds, stones, ounces, and grams, converted together.
Litres, millilitres, and both the US and imperial gallon, pint, and fluid ounce.
Celsius, Fahrenheit, Kelvin, and Rankine, with the offset handled properly.
Cups to grams by ingredient, across US, metric, and imperial cup sizes.
MB, GB, TB and their binary twins MiB, GiB, TiB — both answers, side by side.
US, UK, EU, and Japanese shoe sizes from one foot length.
US, UK, and EU clothing sizes anchored to real body measurements.
Reduce a resolution to its ratio, scale it, and get the pixel density.
About these tools
Every converter here defines its units by their exact size in one base unit and derives each pair from that, rather than storing a table of conversion factors between pairs. It sounds like a detail and it is the difference between a converter that stays internally consistent and one that drifts: the metric-imperial constants are exact by international definition — an inch is exactly 25.4 mm, a pound exactly 0.45359237 kg — so a result that terminates shows exactly rather than as a rounded approximation.
Three of these tools are deliberately not simple multiplications. Temperature is affine, because Celsius and Fahrenheit disagree about where zero sits as well as how big a degree is, and getting that wrong is silent — it produces a plausible temperature rather than an obvious error. Cooking measures need the density of a specific ingredient, because a cup is a volume and a gram is a mass; a cup of flour and a cup of honey differ by nearly a factor of three. And shoe and clothing sizes have no formula at all — they are published conventions, so those tools show the whole chart with your row highlighted rather than presenting one number as fact.
Where a conversion is genuinely ambiguous, both answers are shown rather than one being chosen for you. A US gallon and an imperial gallon share a name and differ by 20%. A megabyte is a million bytes to a drive manufacturer and 1,048,576 to Windows. Picking a side quietly would be wrong for half the people who ask.
None of it touches a server. The unit tables ship with the page and the arithmetic runs in your browser, which is why results update as you type.
FAQ
Are these conversions exact?
The constants are exact wherever an exact definition exists — the inch, the pound, the litre, and the byte all have them. Results are shown to seven significant figures, so a value that terminates displays exactly and one that does not is rounded only at the last digit shown. The exceptions are the ingredient densities and the shoe and clothing charts, which are published averages and conventions, and are labelled as such.
Why do I have to pick an ingredient to convert cups to grams?
Because a cup measures volume and a gram measures mass, and converting between them requires knowing the density of what is in the cup. One US cup is 125 g of flour, 200 g of sugar, or 340 g of honey. A converter that gave a single answer would be assuming an ingredient without telling you.
Is a US gallon the same as an imperial gallon?
No — 3.785 litres against 4.546, about 20% apart. The two systems share names for most of their volume units without sharing values, so the volume converter lists them under separate headings rather than mixing them in one list.
Why does my 1 TB drive show as 931 GB?
The drive holds a decimal terabyte — 1,000,000,000,000 bytes — and your operating system divides by 1,073,741,824 to get gibibytes while still labelling them "GB". Nothing is missing; two unit systems are sharing one set of names. The data storage converter shows both readings side by side.
Can I trust the shoe and clothing size charts?
As a starting point. Neither is standardised by any authority, and brands routinely differ by up to a full size against any published chart. Both tools let you work from a body measurement instead, which is the only value in either chart that means something fixed.