About this tool
The Weight & Mass Converter changes one value into every common metric and imperial mass unit simultaneously. Enter a number, choose your starting unit, and the grid shows milligrams, grams, kilograms, metric tonnes, ounces, pounds, stone, US short tons, UK long tons, carats, grains, troy ounces and pennyweights all at once.
Conversion is linear with the gram as the base unit. Each unit records how many of it are in one gram, anchored to the exact definition 1 pound = 453.59237 g. From there ounce = pound ÷ 16, stone = 14 pounds, short ton = 2000 pounds, long ton = 2240 pounds, carat = 0.2 g and grain = 64.79891 mg. The value is first converted to grams (value ÷ source factor) and then multiplied by each target factor, giving exact, drift-free results.
All computation happens in your browser with plain JavaScript — nothing is uploaded and it works offline. Note that these are units of mass; on Earth's surface they map directly to weight. Extremely small or large results appear in scientific notation while everyday values are rounded to six decimals, and the unit you entered is outlined in the grid.