Imperial system

The Imperial system was first defined in the British Weights and Measurements Act (which was refined up until 1959). Unlike the metric system (also known as Système international or SI units) the imperial system is not based on factors of ten.


Thou, inch, foot, yard, chain, furlong, mile, league are units used when measuring length.

  • 1 thou (th) (0.0254mm in the metric system)
  • 1 inch (in) is equal to 1000 thou (25.4mm)
  • 1 foot (ft) is equal to 12 inches (304.8mm)
  • 1 yard (yd) is equal to 3 feet (914.4mm)
  • 1 chain (ch) is equal to 22 yards (20.1168m)
  • 1 furlong (fur) is equal to 10 chains (201.168m)
  • 1 mile (mi) is equal to 8 furlongs (1 609.344m)
  • 1 league (lea) is equal to 3 miles (1 828.032m) (no longer an offical unit in any nation)


The most common unit used exclusively for area is acre.

  • 1 acre is equal to 1 furlong x 1 chain (0.4047 hectares)


Fluid ounce, gill, pint, quart and gallon are used when measuring volume. Imperial units for volume are different to the US measures.


Grain, drachm, ounce, pound, stone, quarter, hundredweight and ton are units for mass.

  • 1 ounce (oz) is equal to one sixteenth of a pound (28.349 523 125g). There are 16 ounces in 1 lb.
  • 1 pound (lb) (453.592 37g)
  • 1 stone (st) is equal to 14 lb (6.350 293 18kg)
  • 1 hundredweight (cwt) is equal to 112 lb (50.802 345 44kg) (100 lb in the US)
  • 1 ton (t) is equal to 2240 lb (1 016.046 9088kg) (2000 lb in the US)

See also


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