Admittedly, I was going by Wikipedia and r/SpaceX. The latter tended to imply that the source was conversations with employees, but I don't know of a quotable s

Admittedly, I was going by Wikipedia and r/SpaceX. The latter tended to imply that the source was conversations with employees, but I don't know of a quotable source either. So might in fact be wrong. Elon tweeting something that might imply the same size of the engine, albeit with a qualifier (»Chamber pressure is almost 3X Merlin, so engine is about the same size for a given area ratio«). Naïvely dividing booster diameter by the number of engines across the diameter yields 1.2 m for Merlin 1D and 1.7 m for Raptor (although the ITS seems to have a bit of space around the center cluster since only those gimbal).