British standard ordnance weights and measurements

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The British standard ordnance weights and measurements for the artillery were established by the Master General of Ordnance in 1764, and these were not altered until 1919[citation needed] when the metric system was additionally introduced.

This system has largely been replaced by a calibre system, which is the standard today for most weapon systems in use by the world's armed forces.

The 18th century standards were based on projectile weight, and dated back to use of muzzle loaded cannons which fired solid cannonballs. The designations bore only an approximate relationship to the actual weight of the projectile when it was applied to modern artillery.

The table below lists the metric and Imperial calibres of various British weapons, which utilised the standard after 1919:

Name Type Calibre
Metric Imperial
1 pounder "pom pom" Infantry gun/AA gun 37 mm 1.457 inch
2 pounder Anti-tank gun 40 mm 1.575 inch
QF 2 pounder naval gun Anti-aircraft gun 40 mm 1.575
3 pounder Naval gun 47 mm 1.85 inch
6 pounder Anti-tank gun 57 mm 2.244 inch
BL 10 pounder Mountain Gun Mountain gun 69.8 mm 2.75 inch
12 pounder Light field gun 76.2 mm 3 inch
13 pounder Light field gun 76.2 mm 3 inch
15 pounder Field gun 76.2 mm 3 inch
17 pounder Anti-tank gun 76.2 mm 3 inch
18 pounder Field gun 83.8 mm 3.3 inch
Ordnance QF 20 pounder Tank gun 83.8 mm 3.3 inch
25 pounder Gun-howitzer 87.6 mm 3.45 inch
Ordnance QF 32 pounder Tank gun 96 mm 3.78 inch
60 pounder Heavy field gun 127 mm 5 inch


  • Rottman, Gordon L.: Elite 124 - World War II Infantry Anti-Tank Tactics, Osprey publishing, ISBN 1-84176-842-1 p.16