Historical units
Pick a unit and a quantity, and it is converted into today’s units. Filter by what is being measured to see only length, area, volume, mass, count or time.
That is
2.54 cm
1 inch (imperial)
The other way round: 1 m is 39.3701 inches.
- Period: 1959 to today
- Region: the UK
Every unit, smallest to largest
| Unit | That is | Period | Used for |
|---|---|---|---|
| Length | |||
| inch | 2.54 cm | 1959 to today | the UK |
| foot | 30.48 cm | 1959 to today | the UK |
| yard | 91.44 cm | 1959 to today | the UK |
| ell | 1.143 m | c. 1200 to 1824 | cloth and linen |
| fathom | 1.829 m | medieval to today | soundings, rope, timber, mine shafts |
| rod | 5.029 m | c. 1300 to today as an archaic unit | land survey, allotments |
| chain | 20.12 m | 1620 to today as an archaic unit | land survey, railways |
| furlong | 201.2 m | pre-Conquest to today | open-field farming, horse racing |
| mile | 1.609 km | 1593 to today | England, later the UK |
| nautical mile | 1.852 km | 1929 onwards, adopted by the UK in 1970 | navigation and aviation |
| Area | |||
| rood | 1,012 m² | c. 1300 to the 20th century | land, allotments |
| acre | 4,047 m² | c. 1300 to today | farmland |
| hide | – | 7th century to the 12th | taxation |
| Volume | |||
| pint | 568.3 ml | 1826 to today | the UK |
| gallon | 4.546 l | 1826 to today | the UK and the Empire |
| peck | 9.092 l | 1826 to the 20th century | grain, potatoes, apples |
| bushel | 36.37 l | 1826 to the 20th century | grain, fruit, coal |
| firkin | 40.91 l | 1826 to today | beer and ale |
| barrel | 163.7 l | 1826 to today | beer |
| hogshead | 245.5 l | 1826 to today | beer |
| quarter | 290.9 l | medieval to the 20th century | grain |
| tun | 953.9 l | 15th century to 1826 | wine imports, ship capacity |
| Mass | |||
| grain | 64.8 mg | c. 1300 to today | bullets, gemstones, pharmacy |
| troy pound | 373.2 g | medieval to 6 January 1879 | coin, bullion, apothecaries |
| pound | 453.6 g | 1959 to today | general trade |
| stone | 6.35 kg | 1389 for wool, general from 1824 to today | wool, livestock, body weight |
| hundredweight | 50.8 kg | medieval to the 20th century | coal, cement, agricultural produce |
| ton | 1.016 t | medieval to today in restricted use | shipping, coal, iron |
| Count | |||
| dozen | 12 | medieval to today | eggs, buns, small goods |
| quire | 25 | 1706 to today | paper |
| Time | |||
| watch | 4 h | 17th century to today | ships |
How it works
A historical unit rarely has a single value. Before 1826 England used three different gallons at once: the wine gallon of 231 cubic inches, the ale gallon of 282 and the Winchester corn gallon of about 268.8. Each unit here therefore carries its values side by side, with the period, the region and the goods it applied to. Nothing is averaged.
The Weights and Measures Act 1824 swept the old capacity measures away and created the imperial gallon, defined as the volume of ten pounds of water. Everything modern rests on three exact definitions in Schedule 1 to the Weights and Measures Act 1985: the yard is 0.9144 metre, the avoirdupois pound is 0.45359237 kilogram and the imperial gallon is 4.54609 cubic decimetres. Every figure on these pages is computed from those three numbers unless it says otherwise.
Some units never had one size. Medieval England measured land with perches from 15 to 25½ feet depending on the manor, and Scottish units rest on a value for the Scots ell that the sources still disagree about. Where that is the case the range is shown with a note, rather than a single figure that would look more certain than it is.
Counting units belong here too. A score, a dozen, a gross, a quire and a ream count things, so they convert into a number rather than into metres or kilograms.
Imperial units are not quite gone. The mile, yard, foot and inch remain lawful for road signs, draught beer and cider are still sold in pints, and gold is still traded by the troy ounce.