To convert between different imperial weight units select the unit from the unit drop down and enter the amount in the amount box. Alternatively to select other conversion select the type of weight from the top drop down boxes.

Imperial Weight Units

The imperial system of weights, or more correctly the avoirdupois system of weights is the standard system of weight in the United States and is still in common usage in the United Kingdom. The system is based on a pound (lb) of 16 ounces (oz). Nowadays the avoirdupois pound is defined in terms of the kilogram as being exactly 0.45359237 kilograms. Previously standard pound weights were held by the British treasury.

Since the independence of the United States there have been slight changes to the avoirdupois weight system in the UK and so the US system became the American Customary System, however the basic units such as the pound and the ounce are still the same in the American Customary System as in the British Imperial System.

British Imperial Weights

Before the time of Elizabeth the first, the avoirdupois system of weights was in development and many changes in units and their values were made. The last major change in the system came in Elizabethan times, this included the addition of the troy grain and the definition of the pound as 7,000 grains.

Table of Units

US Customary Units

The US customary system of weights is based on the British system at the time of independence, many units remain the same between the two systems however there are differences. The differences include the stone not being included in the US system as it was only formerly included in the British system in 1824. Also the hundredweight in the US customary system is defined as 100 lb and the ton and quarter are also based on a hundredweight of 100 lb, whereas the in the British system the hundredweight is equivalent of 8 stone (112 lb). There remains some confusion as to whether the 100 lb hundredweight was ever in use in the UK before the introduction of the stone.

Table of Units