After a couple of months of research for other projects, I returned to the reductions after the War of the Spanish Succession (see also my Half-Pay officers for 1714). Here I looked into the question on the size of a regiment. More in particular, and do keep it simple, the size of a regiment of foot.
Anyone, including me, with some knowledge of the British army, and the Marlburian period, would probably answer that a regiment numbered 13 companies with one of grenadiers.
However, a careful look at the establishment lists of the armies between 1701 and 1712 reveals a variation that must have given contemporary quartermasters severe headaches. And it gives some nice number-crunching.
Let's use the estimate for the armed forces for 1711 as an example (see the Calendar of Treasury Books):
In the Guard & Garrisons, i.e., the regiments serving in England or in garrison on the colonies we have regiments of 760, 809, 834, 876, and 951 men. Judging from the reductions, the regiments were all established with 12 companies.
In the army in Flanders we find regiments of 938 and 876 men. The ones with 938 men were definitely established with 13 companies, the ones with 876 men most likely.
When we move to the Iberian Peninsula, the situation was as worse as at home: regiments of 725, 785, 834, 845 and 876 men. All regiments appear to have been established with 12 companies.
After the reductions of 1712-14 we find the following establishments:
at Dunkirk, 669 men to a regiment of foot with 12 companies
in Flanders 613 to a regiment with 12 companies
at Minorca 625 men with 12 companies
at Gibraltar 500 with 12 companies
In England/Scotland, including the West Indies, 445 men with 10 companies
in Ireland, 444 men, also in 10 companies
(the one man difference between England and Scotland was the Quarter-Master, for whom was no room on the Irish Establishment).