About HowManyInOne
HowManyInOne answers one measurement question per page, puts the answer in the first line, and gets out of the way.
Why This Site Exists
Most conversion sites make you fill in a form before they tell you anything, then bury the answer under advertising. If you are standing in a kitchen with flour on your hands, or in a hardware store with a phone in one hand, that is the wrong design. Every page here states the answer immediately, in plain language, and the page is small enough to load on a weak connection.
The second reason is accuracy. A surprising number of conversion pages use rounded constants — 2.2 pounds to a kilogram, 30 milliliters to a fluid ounce — without saying so. Those shortcuts are fine for a mental estimate and wrong for anything that has to fit, fill or dose. We use the exact legal definitions and say when a value is exact.
How the Values Are Checked
Every unit on the site is defined once, in a single data file, as an exact factor relative to a base unit: the meter for length, the kilogram for weight, the liter for volume and the kelvin for temperature. The 27 units and 52 conversion pages are all generated from that one source, so no page can disagree with another.
That data file is covered by an automated test suite which runs on every build. It checks known benchmarks — 5,280 feet to a mile, 16 tablespoons to a cup, 32 °F equal to 0 °C — and verifies that converting any unit to any other and back returns the original value. A second suite checks the pages themselves: that no two pages share a title, that every page links to at least five others, and that the number in each page title matches what the arithmetic actually produces. If any of those fail, the site does not build.
The full list of definitions and rounding rules is on the how we calculate page.
Who Is Behind It
HowManyInOne is built and maintained by Ewald, an independent software developer. It is not backed by a publisher or a content network, and nothing on it is written by filling a template with synonyms. Each page's context, pitfalls and examples are written by hand, which is why the site covers a few dozen conversions properly rather than ten thousand badly.
Corrections
If a number here is wrong, or a page is missing context that would have helped you, please say so. Corrections are the fastest way to make the site better — email hello 'at' howmanyinone.com or use the contact page. Reports about a specific value are especially welcome; include the page and what you expected.
What Is Coming
Area, speed, time, digital storage, pressure and fuel economy are next, along with ingredient-level cooking conversions (cups of flour to grams, which depends on the ingredient) and a handful of everyday calculators. Each will have to meet the same bar: the answer first, the formula shown, and a test proving the number.