The population of India during the British Raj days was first counted during the census of 1871. Prior to this a full census and data on British subjects were not available. The 1891 census also did a linguistic division, but nothing such as "British Subjects". But people who spoke English as a mother tongue returned 238,409.
The total Number of people with English as mother tongue, in India in 1891 as per the 1891 census was 238,409.
The total Number of British subjects in India in 1921 as per the 1921 census was 165,485.
The 1931 census was was the last census that was not subject to inaccuracies. The 1941 census was hampered by war and self-return from an illiterate populace.
The European British subjects totalled 155,555 of whom 110,137 were
males and 45,418 females. Of these again 7,205 males and 3,422 females
were found in Burma, and while in Burma the figures show a total
increase of 1,434 males and 1,365 females since 1921, the figures for
India proper show a further fall since 1921 and are now little more
than 80 per Cent. of those recorded in 1911, while males taken alone
are fewer than in 1901.
Reference from census record.