The Imperial System, also known as the British Imperial System, originated in the UK and was the official system of weights and measures used across the British Empire. It came into official use in the 1820s, following the Weights and Measures Act and continued until the UK began transitioning to the metric system in the late 20th century.
Here are the primary units and their equivalents within the Imperial System:
Length/Distance:
- Thou (or mil): 1/1000 of an inch.
- Inch (in): Basic unit of length.
- Foot (ft): 12 inches.
- Yard (yd): 3 feet or 36 inches.
- Chain: 22 yards.
- Furlong: 220 yards or 10 chains.
- Mile (mi): 8 furlongs or 1,760 yards.
Volume:
- Fluid Ounce (fl oz): Basic unit of liquid volume.
- Pint (pt): 20 fluid ounces.
- Quart (qt): 2 pints.
- Gallon (gal): 4 quarts or 8 pints.
- Bushel: Used for dry goods, especially in agriculture.
Weight/Mass:
- Grain (gr): The smallest unit of mass in the imperial system.
- Ounce (oz): 16 drams or 437.5 grains.
- Pound (lb): 16 ounces or 7,000 grains.
- Stone (st): 14 pounds. (This unit is still commonly used in the UK to measure personal body weight.)
- Hundredweight (cwt): 112 pounds (long hundredweight). There was also a short hundredweight used in the U.S., which was 100 pounds.
- Ton: 20 hundredweight or 2,240 pounds.
Temperature:
- Fahrenheit (°F): A temperature scale where 32°F represents the freezing point of water, and 212°F represents its boiling point at sea level under standard atmospheric conditions.
It’s worth noting that there are some differences between the Imperial System and the U.S. Customary System, especially in terms of volume measurements. For instance, a U.S. gallon is smaller than a UK (imperial) gallon.
Although the UK has largely transitioned to the metric system, remnants of the Imperial System are still encountered, especially in specific contexts like road distances (measured in miles) and the sale of draught beer and cider by the pint.