What Is the Difference Between 4.5, 10.5 and 13.5 Tog Duvets?

Most of us know something about how togs work. During the winter, you want a higher tog duvet, and when summer comes around, you can dig into the cupboard and bring out the lighter tog. Something like that.

Tog rating is actually one of the most searched duvet questions in the UK, and yet still one of the most misunderstood. While we understand that higher tog = increased warmth, who among us really knows the practical difference between a 4.5 tog, a 10.5 tog, and a 13.5 tog? More importantly, do most people know which one is right for their sleep?

In this guide, we’re going to break down what tog ratings mean, how each weight performs, and how to choose the right one for optimal sleep all year round.

Let’s keep it simple. Tog is just a unit of thermal resistance. It measures how effectively a duvet traps warm air and insulates the sleeper, with higher togs = the most warmth and insulation.

The tog scale runs from 1 to 15, with each rating corresponding more or less to a season or sleep temperature preference. That’s why we often associate tog ratings with seasonal terms - summer, all-season, and winter.

Remember: Tog rating measures warmth only. It doesn’t measure weight, quality, or fill material. A high-quality 4.5 tog duvet and a poor-quality 4.5 tog duvet might have the same thermal resistance, but how they’d feel during sleep would likely differ radically.

When you buy a 4.5 tog duvet, you’re getting a lightweight, low-warmth duvet designed for use during the warmer months or mild temperatures. At 4.5 tog, the duvet provides pretty minimal insulation, so it's ideally suited to summer use, warmer bedrooms, or sleepers who overheat easily. Because it doesn’t have much insulation, this allows your body heat to dissipate rather than get trapped beneath the cover.

Best for: Summer use, warm sleepers, bedrooms that retain heat, or as part of a layering system with a second duvet in winter.

A 10.5 tog duvet is a mid-weight duvet suited to year-round use in most UK bedrooms. It sits in the middle of the tog scale, and is also one of the most commonly purchased tog ratings in the UK.

A 10.5 tog duvet gives you moderate insulation; enough warmth for autumn and spring, and adequate for many sleepers through winter in a centrally heated home. It's definitely not the warmest option available, but for the average UK bedroom temperature you can count on it performing reliably across most of the year.

Best for: Year-round use in temperature-controlled bedrooms, average sleepers who neither run consistently hot nor cold, and as a versatile single-duvet solution.

A 13.5 tog duvet is your more heavyweight option: it’s high-warmth and designed for use during the winter season. It provides significantly more insulation than a 10.5 tog, so if you wake up in the night reaching for more cover in the ‘-ber’ months, the higher thermal resistance of a 13.5 tog can make a measurable difference to your shut-eye.

Best for: Winter use, cold sleepers, unheated or poorly insulated bedrooms, and anyone who consistently finds standard duvets insufficient through the colder months.

A 3-in-1 duvet takes an intelligent approach to the tog system: rather than accepting that no single rating works year-round, it combines a lightweight summer duvet with a mid-weight autumn layer that can be used independently or clipped together for winter. A bit like a hybrid mattress, a 3-in-1 combines two different functions into a single, seasonally intelligent system.

For example, Simba’s Hybrid® 3-in-1 Duvet combines a 3.5 tog summer duvet with a 7 tog spring and autumn duvet. Fastened together, they create a 10.5 tog winter duvet. All three configurations use Stratos® technology in the outer cotton to help regulate temperature, and Simba Renew Bio™ fill for warmth.

This approach removes the need to store and switch multiple duvets across the year, while also making sure that you’re using the right tog rating for the season.