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Mass

Kilograms, pounds and ounces.

Everyday weights sit on a single exact definition: since 1959 the avoirdupois pound has been 0.45359237 kilograms, and every ounce, stone and short ton follows from it. The trap in this category is that more than one system shares the same words — a troy ounce of gold is not the ounce on a kitchen scale, and a fluid ounce is not a mass at all.

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Tell us what is missing and where its numbers should come from.

What should it convert, calculate or generate, and where would the authoritative numbers come from? A link to the standard or publication that defines them is the most useful thing you can send.

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How these tools are built

Every tool in this category runs entirely in your browser: there is no upload, no account and no request to a server once the page has loaded. The numbers behind them are transcribed from the organisation that defines them — NIST for units, the W3C for web formats, the WHO for health measures — and each page names its source next to the formula. A tool whose reference values stop reproducing fails the build and does not ship, which is the whole reason the catalogue grows slowly.

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