The Royal Navy's three-fleet carrier arithmetic

Britain's 330,000-ton allowance could buy ten 33,000-ton carriers, eleven 30,000-ton ships, twelve 27,500-ton ships, or about fifteen at 22,000 tons. The Royal Navy's three-fleet structure made twelve or fifteen attractive because the force could be divided evenly among operating areas. The larger ship used its hangar and maintenance space more efficiently and was more likely to survive against a 33,000-ton opponent. Twelve 27,500-ton carriers, four per fleet, are presented as the best compromise between deck numbers, aircraft capacity, and protection. The tons-per-aircraft method is a reconstructed table checked against calculations being made in the 1920s, so it reflects a contemporary planning approach rather than an official fleet programme. Treaty tonnage functioned as a force-structure budget as well as a cap on individual designs.