Although it cannot be determined exactly how tall William Pitt was, all known references point to him being about six feet in height. At a dinner in late 1804 at which Thomas Lawrence (the famous painter) was present, he observed that Pitt “must be Six feet high” (Farington Diary, Vol. 3: 15).
Another reference to William’s height is found in correspondence from his young manhood. In 1781, Lady Hester Chatham (William’s mother) received a letter from her friend Fanny Boscawen in which Fanny relates a dinner she’d had the previous evening with a lawyer from Lincoln’s Inn. Pitt was a barrister at that time, and was living in the attic chambers of 4 Stone Buildings, Lincoln’s Inn. During the course of the dinner, Fanny was speaking with this unknown lawyer about the Gordon Riots of the previous year, and he told her that “when they form’d themselves into Companies for the defence of the Inns of Court they agreed that the tallest Man shou’d be the Captain: thus Mr. Pitt commanded their Company” (letter from Fanny Boscawen to Hester Chatham dated July 28th, 1781; printed in Birdwood (ed.) 1994: pp. 158-9).
Without specifying Pitt’s exact height, it is still indicative that he was taller than all the other men around him. In an age when the average man was about 5’6”-5’7,” Pitt must have stood out at 6 feet.
Birdwood, V. (ed.) (1994) So dearly loved, so much admired: Letters to Hester Pitt, Lady Chatham from her relations and friends (1744-1801). London: HMSO, pp. 158-9.
Farington, J. (ed. by James Greig) (1924) The Farington Diary, Volume 3. London: Hutchinson, pg. 15.