A carpet tog rating is exactly the same as a tog rating for a duvet - it's how good it is at insulation. The higher a carpet's tog rating, the better it'll be at keeping your room warm, so pick a carpet with a high tog rating if you'll be laying it over draughty wooden floorboards!You need to pay special attention to tog ratings if you've got underfloor heating. Whilst you want to insulate your room, you also want the heat to be able to flow up and into the room. A lower tog rating will transmit underfloor heating more efficiently. We'd recommend a maximum of 2.5 tog on top of underfloor heating. Underlay also has a tog rating, so this could be a combination of a high tog carpet and a low tog underlay, or vice versa.