Units of Measurement
The units behind trade, law and science: troy weight for gold and silver, the inches, rods and furlongs of US linear measure, and the Beaufort scale sailors still use for wind. Each page gives the exact metric value where one exists and the history of where the unit came from.
Every page in unit conversions
- Troy WeightTroy ounces, pennyweights and grains for gold, silver and gems.
- Beaufort ScaleWind force 0 to 12 in mph, knots and km/h, with land and sea signs.
- Linear MeasureInches to leagues: the US and traditional length units, with exact metric values.
About the original tables
From 2002 to 2014 this site published more than 120 tables of historical weights and measures, from apothecaries' weight to regional surveyors' measures. We're rebuilding the most useful of them with sources, starting with the pages people still link to. Links to the old pages lead to their new versions here.
Exact definitions
- 1 inch = 2.54 cm and 1 yard = 0.9144 m (exact, since 1959)
- 1 avoirdupois pound = 453.59237 g (exact)
- 1 grain = 64.79891 mg, the same in troy, avoirdupois and apothecaries' weight
- 1 troy ounce = 480 grains = 31.1034768 g