The British East India Company maintained an armed force large and competent enough to subdue and control Mughal India, but just how large was it? How comparable was it to contemporary national military forces?
The size of these armies underwent tremendous growth as the Company expanded in India and acquired ever more security obligations, before declining when the Indian Mutiny broke out in 1857.
- 1763: 18,000
- 1796: 102,000
- 1857: 271,000
- 1867: 171,000
- 1875: 190,000
(Source: Schmidt, Karl J. An Atlas and Survey of South Asian History. ME Sharpe, 1995.)
The three Presidency armies did not expand uniformly. They were raised according to the local strategic needs of the Company, which changed over time, especially as the Company conquered more of India. Originally, the Madras Army was the largest of the three; however, it stopped growing in strength after 1799, while the Bombay Army's expansion ceased after 1817. Consequently, the Bengal Army became larger than the other two combined.
The Presidency armies were the muscle of the East India Company, which managed to achieved dominance over the subcontinent. Given that achievement, clearly they were comparable to the best forces of their contemporary Indian states.
Originally they weren't very effective fighting forces. The Bengal Army was equipped with European arms, but poorly drilled and lacking discipline. Things changed after the Battle of Plassely, when Clive of India initiated military reforms. He trained them after the regular British fashion, with European officers in command. This proved sufficiently effective that the Madras and Bombay armies soon copied Bengal.
However, the Company treated its forces much in the same way large businesses tended to approach menial labour employees. Insensitivity, low pay, and other HR issues resulted in chronic discontent within the armies. A long history of mutinies by both native and European soldiers and officers stretched back to the 17th century.
: Wikipedia, citing Harold Raugh's The Victorians at War, 1815-1914: An Encyclopedia of British Military History, lists their combined strength as 196,000 in 1876, but this is a small discrepancy.