British weight is a tapestry of agricultural practicality, royal decree and the demands of trade. Before digital scales, the world was measured by the weight of a grain, the heft of a stone, and the burden of a ton.
- The grain: the smallest historical unit, defined by the weight of a single grain of barley, and identical across all three British weight systems.
- The stone: originally a physical stone kept as a standard, and still the preferred unit for body weight in Britain.
- The scruple: a precise apothecary measure used by physicians and herbalists.
- The clove and tod: the working units of the wool trade, measuring the wealth of the countryside.
- The hundredweight and ton: weights born of maritime trade and the industrial revolution.
Need to convert between these ancient weights and modern metrics? Visit our Weight Converter.
Apothecaries’ Ounce (℥)
The dispensing ounce of the pharmacopoeia, identical in weight to the troy ounce but subdivided entirely differently.
480 grains = 31.1035 grams
Apothecaries’ Pound
The nominal top of the apothecaries’ scale, at twelve ounces or 5,760 grains, and identical in weight to the troy pound.
5,760 grains = 373.24 grams
Clove
An old English weight unit used for wool and cheese, representing half a stone.
7 pounds = 3.175 kilograms
Drachm (Apothecary)
An ancient apothecary mass unit equivalent to 60 grains used by chemists to weigh precise ingredients.
3.89 grams
Dram (Avoirdupois)
A standard commercial mass unit equal to one-sixteenth of an avoirdupois ounce.
1.77 grams
Grain (gr)
Based on the weight of a single barley grain, identical across avoirdupois, troy, and apothecary systems.
64.79891 milligrams
Hundredweight (cwt)
The traditional "long hundredweight" of 112 lbs established legislatively by Edward III.
112 pounds = 50.8023 kilograms
Last (Weight)
A traditional medieval wool trade bulk unit representing 12 packs and over 4,000 pounds.
>4,000 pounds
Pack (or Sack)
A traditional wool trade bulk unit representing two weys (240 to 364 pounds of fleece).
240-364 pounds
Pennyweight (dwt)
A traditional troy weight unit equal to 24 grains or one-twentieth of an ounce.
1.56 grams
Quarter (qr)
A quarter of a hundredweight, being 28 pounds or two stone, and a working tier of the coal and produce trades.
28 pounds = 12.7006 kilograms
Scruple (℈)
A tiny apothecary mass unit equal to exactly 20 grains, used by chemists to weigh powdered medicinal ingredients.
20 grains = 1.296 grams
Seam
A traditional packhorse load measure for commodities like glass and wool (200-300 lbs).
200 to 300 pounds
Slug
The imperial unit of mass, defined as that which one pound of force accelerates at one foot per second squared.
Approx. 14.594 kilograms = 32.174 pounds
Stone (st)
The traditional British weight unit equal to 14 pounds, remaining the enduring colloquial choice for measuring personal human body weight.
14 pounds = 6.35029 kilograms
Tod
A historical English wool trade weight unit equal to two stone.
28 pounds = 12.7006 kilograms
Ton (long ton)
The traditional British long ton containing exactly 2,240 pounds.
2,240 pounds = 1,016.047 kilograms
Troy Ounce (ozt)
The precious metal ounce of 480 grains, descended from the weights used at the medieval fairs of Troyes in Champagne.
480 grains = 31.1035 grams
Troy Pound (lb t)
The precious metal pound of twelve troy ounces, or 5,760 grains, and the standard by which English coin was struck after Henry VIII abandoned the Tower pound in 1526.
5,760 grains = 373.24 grams