What Is a Tog Rating?

What Is a Tog Rating? Quick Definition

Tog is a unit of thermal resistance. It measures how effectively a duvet traps warm air — the higher the tog, the warmer you'll sleep. The scale runs from 1 to 15 in practice, though most duvets sit between 4.5 and 13.5. Tog tells you nothing about what's inside the duvet, how heavy it is, or how long it will last. A goose feather 10.5 tog and a hollowfibre 10.5 tog provide identical warmth — the fill type determines feel and laundering, not the tog.

This is the most important correction in any tog guide: tog is a warmth measurement, not a quality score. Two duvets can share the same tog rating and feel completely different under the same conditions, because everything except warmth is determined by the fill, the weight, and the construction.

What the Numbers Mean in Practice

4.5 tog — summer, warm sleepers, well-heated bedrooms. Lightweight and minimal — the equivalent of a sheet with insulation.

10.5 tog — the UK year-round default. The most widely sold rating across hospitality and home because it covers the middle ground without overheating in mild conditions or leaving you cold in a dip.

13.5 tog — winter, cold sleepers, older buildings with poor insulation or unheated guest rooms. The right choice when a colder room needs the duvet to do more of the work than the heating does.

15 tog — maximum warmth for very cold sleepers or unheated rooms. Not commonly stocked in hospitality settings because most guest rooms have heating — but available for care homes and cold-climate settings.

What Tog Doesn't Tell You

Tog doesn't measure weight. A 13.5 tog goose feather duvet is noticeably lighter than a 13.5 tog hollowfibre duvet, because natural down traps warm air more efficiently per gram of fill. Same warmth, very different weight in the hand.

Tog doesn't measure laundering requirements. A 10.5 tog hollowfibre is machine washable in most domestic or commercial machines. A 10.5 tog goose feather and down duvet needs a large-capacity machine and careful drying. The tog is identical — the care requirement is not.

For the full breakdown of which tog suits which setting, sleeping pattern, and commercial use case, read our Tog Rating Guide. Ready to order? Browse duvets by tog rating.