Ds (20mo) is going into his new big bed next week (once dh and i have put it together). What tog duvet should he have? he sleeps in a 2.5tog sleeping bag at the moment and a thick duvet seems very thick compared to his sleeping bag. However a 4.5 tog duvet doesn't look thick enough to keep him warm.
His sleeping bags are getting very small for him so will need to move him out of these very soon.