Imperial units

The Imperial units or the Imperial system is a collection of measurement units. An Act of Parliament in 1824 created it from traditional English units. The United Kingdom and Commonwealth countries (which were once part of the British Empire as British colonies) used this system from 1824 until they changed to the metric system in the second part of the 20th century. The Imperial system is very similar to the American system but there are some differences.

In 2019 Boris Johnson proposed changes to the law in the United Kingdom to increase the use of Imperial units.  He said this would be a benefit of Brexit. In 2023 the idea was dropped when  98.7% of people said they preferred using metric units. The law was changed to permit wine to be sold in pints. 

 Length 
   inch              link              foot             yard        pole chain             furlong           mile             league metre 1 inch 1                                         0.0254 1 link 7+  1                                 0.201168 1 foot 12                1+  1                                   0.3048 1 yard 36                4+   3                1                            0.9144 1 pole 198               25                16+  5+   1                      5.0292 1 chain 792               100               66               22               4 1                         20.1168 1 furlong 7,920             1,000             660              220              40 10                1                   201.168 1 mile 63,360            8,000             5,280            1,760            320 80                8                 1           1,609.344 1 league 190,080           24,000            15,840           5,280            960 240               24                3                1 4,828.032

The British nautical mile used to be 6080 feet. In 1970 the UK adopted the international definition of 1852 metres.

 Measures of area 
DerivedSquare rods (sq poles)Square milesSquare feetHectares (Metric)Square Metres (Metric)1 square foot = 1 foot x 1 foot  = 0.003673095square rods  = 0.00000003587square mile  = 1 square foot  = 0.000009289257 ha  = 0.09290304 m²1 perch = 1 rod × 1 rod    = 1 square rods   =  square mile  = 272.25 square feet  = 0.002529 ha  = 25.29285264 m²1 rod = 1 furlong × 1 rod    = 40 square rods   =  square mile  = 10890 square feet  = 0.10117141056 ha  = 1011.7141056 m²1 acre  = 1 furlong × 1 chain  = 160 square rods  =   square mile   = 43560 square feet  = 0.40468564224 ha  = 4046.8564224 m²

 Volume 
+ Liquid   ounce    gill        pint         quart        gallon litre 1 (fluid) ounce 1          0.028 413 1 gill 5        1            0.142 065 1 pint 20       4           1          0.568 261 1 quart 40       8           2             1       1.136 522 1 gallon 160      32          8             4           1 4.546 09

+ Dry 1 peck                              =   2 gal  = 9.092 18 L 1 kenning or bucket                =  2 pecks    =   4 gal  = 18.184 36 L 1 bushel = 2 kennings   =  4 pecks    =   8 gal  =     36.368 72 L 1 strike                =  2 bushels  =  16 gal  =   72.737 44 L 1 quarter or pail                =  8 bushels  =  64 gal  =  290.949 76 L 1 chaldron = 4 quarters   = 32 bushels  = 256 gal  = 1163.799 04 L 1 last = 10 quarters  = 80 bushels  = 640 gal  = 2909.497 6 L

+ Brewery 1 firkin                            =  9 gal  =  40.914 81 L 1 kilderkin                = 2 firkin  = 18 gal  =  81.829 62 L 1 barrel = 2 kilderkin  = 4 firkin  = 36 gal  = 163.659 24 L 1 hogshead  = 3 kilderkin  = 6 firkin  = 54 gal  = 245.488 86 L

The full table of British apothecaries’ measure is:
+ Apothecaries’ measure 1 minim                             = 0.059 193 880 208¯3 mL 1 (fluid) scruple               = 20 minims   = 1.183 877 604 1¯6 mL 1 (fluid) dram or fluidram  = 3 scruples  = 60 minims   = 3.551 632 812 5 mL 1 fluid ounce  = 8 drachms   = 480 minims  = 28.413 062 5 mL 1 pint                = 20 ounces   = 568.261 25 mL 1 gallon  = 8 pints     = 160 ounces  = 4.546 09 L

For a comparison to the United States customary units see the article on Comparison of the Imperial and US customary systems.

 Mass and weight 
 1 grain                                    =           64.798 91 mg 1 drachm  = 1/16 ounce       = 1/256 pound  =        1.771 845 195 312 5 g 1 ounce                     = 1/16 pound   =       28.349 523 125 g 1 pound  = 7000 grains                     =      453.592 37 g 1 stone                     =   14 pounds  =    6.350 293 18 kg 1 quarter  = 2 stone          =   28 pounds  =   12.700 586 36 kg 1 hundredweight  = 4 quarters       =  112 pounds  =   50.802 345 44 kg 1 ton  = 20 hundredweight = 2240 pounds  = 1016.046 908 8 kg

Related pages
 International System of Units

 Other websites 
 Canada - Weights and Measures Act 1970-71-72 
 British Weights And Measures Association 
 Jacques J. Proot's Anglo-Saxon weights & measures  page.
References