Conversions Between Imperial Weight Units

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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

Unit Abbreviation As Pounds As Kilos Notes
grain gr 1/7000 0.0000648kg As troy grain - introduced by Elizabeth I
dram dr 1/256 0.001772kg Defined as 1/16th of an ounce previously known as the "part"
ounce oz 1/16 0.0283kg Commonly used in US and UK recipes
pound lb 1 0.45359237kg Base unit of avoirdupois system
stone st 14 6.35kg Not used in the US customary system
quarter qtr 28 12.70kg Equivalent of 2 stone or a quarter of a hundredweight
hundredweight cwt 112 50.80kg Defined as 8 stone in the British Imperial system
ton t 2240 1016kg Known as the long ton to differentiate from the US short ton

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

Unit Abbreviation As Pounds As Kilos Notes
grain gr 1/7000 0.0000648kg As troy grain
dram dr 1/256 0.001772kg Defined as 1/16th of an ounce
ounce oz 1/16 0.0283kg Common between the US and UK systems
pound lb 1 0.45359237kg Base unit of avoirdupois system
quarter qtr 25 11.34kg Equivalent of a quarter of a hundredweight
hundredweight cwt 100 45.36kg Differs from the British hundredweight by 12 lbs
ton t 2000 907.2kg Known as the short ton to differentiate from the long ton