UnitBench

One value, every unit at once

No pair of dropdowns. Type a number and read every unit in the category — click any one to make it the input.

Click any tile to make it the input — the value carries across.

The two-dropdown problem

Every converter works the same way: choose a from-unit from a list of forty, choose a to-unit from another list of forty, read one number. That is fine for a single lookup, and a single lookup is the one case where you would have used the search bar instead.

The case where a tool earns its place is repeated conversion — working through a recipe, a spec sheet, a shipping manifest — and there the dropdowns are pure friction. So this shows the whole category at once. One number in, every unit out, and clicking a result makes it the new input with its value carried over.

Units that share a name and are not the same

The gallon is the notorious one. A US gallon is 3.785 litres; an imperial gallon is 4.546. That is a 20% difference, and it is why American and British fuel-economy figures are not comparable without conversion. The fluid ounce differs too — and, awkwardly, in the opposite direction, with the imperial fluid ounce being the smaller of the two relative to its pint.

Then there is the ton: 907 kg short, 1016 kg long, 1000 kg metric. Any converter that offers a single unlabelled "gallon" or "ton" is guessing on your behalf, and it will be wrong for roughly half its users. Both are listed here, labelled.

Where a defined exact value exists, it is used exactly. The inch has been precisely 25.4 mm since the international yard and pound agreement of 1959, and the pound precisely 0.45359237 kg. Converters that use rounded approximations for defined constants disagree with each other in the fourth decimal place for no reason at all.

Where the maths is different

TemperatureNot a ratio — it has an offset, so it works differentlyData sizesWhy your 1 TB drive shows up as 931 GBCooking measuresA cup of flour and a cup of water do not weigh the same

Questions

Why is there no long list of individual conversion pages?
Because they would be worthless to you and to us. A page for every unit pair is hundreds of near-identical pages differing by one noun, which is the definition of thin content — and Google answers "5 km in miles" directly in the results anyway, so nobody clicks through. What is actually useful is a surface where one value updates every unit at once, which is what this is.
Why does clicking a tile change the input?
Because conversion is rarely a single step in practice. You convert a spec from inches to millimetres, then realise you want it in centimetres, then in feet. Two dropdowns make that three separate operations. Here the tile you click becomes the source with its value carried across, so you can walk through units as fast as you can read them.
How precise are the numbers?
The factors are the exact defined values wherever one exists — an inch is exactly 25.4 mm and a pound exactly 0.45359237 kg by international agreement, not approximations. Results are shown to a sensible number of significant figures rather than a fixed number of decimals, so both very small and very large results stay readable without implying precision that is not there.
Why are there two gallons and two fluid ounces?
Because they are genuinely different units that share a name. A US gallon is 3.785 litres and an imperial gallon is 4.546 — a 20% difference, which is enough to ruin a fuel-economy calculation or a recipe. Rather than silently picking one, both are listed and labelled. The same applies to the ton and the fluid ounce.
Is anything sent to a server?
No. The conversion factors are in the page and the arithmetic runs in your browser. There is no analytics script and no request after the page loads.