I've looked around the internet and read Ashley Jackson's "The British Empire and the Second World War," but I can't seem to find a source stating how many total troops from the Empire served during World War 2.
OK, this is easier said than done probably, but I'll try. These are the figures for Total Mobilized, all branches, as given in World War II: Encyclopedia of Facts and Figures by John Ellis, for the the major components of Britain's reach.
| County | Total Mobilized |
|---|---|
| Australia | 993,000 |
| Canada | 1,100,000 |
| India | 2,581,800 |
| New Zealand | 192,800 (This is active strength, c. 1945. Total mobilized is not given) |
| South Africa | 250,000 |
| United Kingdom | 5,896,000 |
| Total | 11,013,600 |
So that is at least a rough number, but I can't vouch for its completeness. I'm not sure whether the UK's numbers, for instance, include all of the minor possessions and what not. For instance, a quick check on Wiki shows that nearly 100,000 Kenyans served, and I can't say whether that is part of the 5,896,000, or needs to be added to the total.