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Converters

Converters

Five converters, each covering a family of units that genuinely belong together. The mistakes people make in this category are rarely arithmetic — they are reaching for the wrong base system or forgetting that a "convert" question sometimes has more than one honest answer.

The unit converter handles the everyday physical quantities: length, mass, volume, area, speed and temperature. Most of its factors are exact by international agreement — an inch is exactly 25.4 millimetres, a pound is exactly 0.45359237 kilograms — but a few, like some historical or regional measures, are approximate. The tool is honest about which is which rather than presenting every figure with the same false precision. Temperature is a separate case entirely, since converting between Celsius, Fahrenheit and Kelvin involves an offset, not just a multiplication, so it is handled on its own path.

The data storage converter looks like it belongs in the same tool as length and mass, but it needs a switch the others don't: storage has two competing definitions of "kilo." Drive manufacturers count in units of 1000 (a decimal terabyte), while operating systems often report in units of 1024 (strictly a tebibyte). That is the entire reason a "1 TB" drive shows up as roughly 931 GB in your file manager — nothing is missing, the two sides are just counting differently, and the gap widens at every step up.

The time zone converter and number base converter are conversions in a looser sense — one maps a moment in time across places that each choose their own offset (some, like India and Nepal, by 30 or 45 minutes rather than a full hour), and the other maps a quantity across counting systems rather than physical units. Daylight saving makes the time zone tool the trickiest of the five: twice a year, in the transitioning region, a local time either does not exist or happens twice, and the tool has to say so rather than silently picking one.

The colour converter rounds the set out — HEX, RGB and HSL describe the same colour space three different ways, useful for design work rather than physical measurement, and it is the one converter here that also computes something derived (contrast ratio) rather than only reformatting the input.