What tog duvet do I need?

[boopdoop]

I need to move my DS (21 months) into a bed next week and so need to get a duvet for him (has been in sleeping bags) but I have no idea which tog to buy. I have to tree them online, so can't see what they seem like in the shop. What should I get?! His room is not too cold, around 19 degrees usually at this time of year. Thank you.

[boopdoop]

Buy them online not tree them!!!

[soundsystem]

I've just moved DD into a bed and got her a 7.5 tog one - from what I read between 4 and 10 tog is ideal for kids duvets (I feel a bit mean as I have a 13.5 tog one myself, but something to do with smaller bodies/duvets keeping in more heat, and she seems happy enough with it!).

Her room is around 17 degrees at the moment and she has fleecy PJs, a blanket and then the duvet, although she mostly ends up on top of the duvet.

[boopdoop]

Thanks sound, really helpful.