In the days well before photography was even a word in the English language, people had to rely solely on portraits, silhouettes, and miniatures to even come close to depicting a person’s physical features. In short, these likenesses were a mere close approximation at the best of times. Therefore, I intend to compile various accounts of Pitt’s physicality through the eyes of his observers.
Arguably, the first published biography of Pitt by Henry Cleland (1807) does this in a concise, effectual way:
"His person was tall and slender, his complexion rather fair, with blue eyes, large forehead, and prominent features; his countenance was strong, thoughtful, and rather stern, except when enlivened by some sudden impulse" (Cleland, 1807: 337).
By all accounts, Pitt was tall and thin.
Cleland, H. (1807) Memoirs of the Life of the Right Honourable William Pitt. London: Albion Press, p. 337.