Weights and Measures
Imperial Measurement Gauge in Trafalgar Square
Modified Photo taken by Matt Brown via Wikimedia (CC BY 2.0)
Over the centuries the UK has used various terms and systems of weights and measures. Some terms had local variations in the size or quantity of the unit and some systems were used by different trades or professions for example:
- Avoirdupois Weight was the widely used everyday system of measurement.
- Apothecaries’ weight was used by doctors and chemists for medicines.
- Troy weight was used for precious metals.
- Jewel Weight was used to measure precious stones.
We will concentrate on the everyday system commonly referred to as the Imperial or avoirdupois system.
| Measurement | Is called | Approx. Metric Equivalent |
| Weight | ||
| 16 drams | 1 ounce (oz) | 28.35 grams |
| 16 ounces | 1 pound (lb) | 453.59 grams |
| 14 pounds | 1 stone (st) | 6.35 Kg |
| 2 stones | 1 quarter (qtr) | 12.7 Kg |
| 4 quarters (112 lb) | 1 hundredweight (cwt) | 50.8 Kg |
| 20 hundredweight (2240 lb) | 1 ton (Imperial) | 1016.05 Kg |
| Length | ||
| 3 barleycorns | 1 inch (in or “) | 254 mm or 2.54 cm |
| 7.92 in | 1 Llnk | 20.11 cm |
| 12 inches | 1 foot (ft or ‘) | 30.48 cm |
| 3 feet | 1 yard (yd) | 91.44 cm |
| 5½ yards | 1 perch, pole or rod | 5.03 m |
| 100 links (4 poles, 22 yards or 66 feet) | 1 chain | 20.12 m |
| 40 poles (10 chains) | 1 furlong | 201.17 m |
| 8 furlongs (80 chains) | 1 mile | 1.61 km or 1609.34m |
| 1.15 miles | 1 nautical mile | 1.85 km |
| 3 miles | 1 league | 4.83 km |
| Volume | ||
| 20 minims | 1 fluid scruple | 1.23 ml |
| 3 fluid scruples | 1 fluid drachm | 3.55 ml |
| 8 fluid drachms | 1 fluid ounce (fl. oz.) | 28.41 ml |
| 5 fluid ounces | 1 gill | 14.21 ml |
| 4 gills (20 fluid ounces) | 1 pint | 568.26 ml |
| 2 pints | 1 quart | 1.14 l |
| 4 quarts | 1 gallon | 4.55 l |
| 2 gallons | 1 peck | 9.09 l |
| 4 pecks | 1 bushel | 36.38 l |
| Area | ||
| 144 square inches | 1 square foot | .09 square metre |
| 9 square feet | 1 square yard | .84 square metre |
| 30¼ square yards | 1 perch | 25.29 square metre |
| 40 perches | 1 rood | 1011.71 square metre |
| 4 roods | 1 acre | 4046.86 square metre or .40 Hectare |
| 640 acres | 1 square mile | 2.59 square km or 259 Hectares |
The University of Nottingham have some excellent pages on weights and measures and so rather that reinventing the wheel I will just provide links to them.
The Maths Salamanders website has some useful and downloadable conversion tables for personal use.
Peter Reed 2022