Bedroom · Explainer · 4 min ·
What tog duvet do you need? Slide the room temperature and see
The tog on a duvet label tells you how warm it is, and the right one depends on your bedroom, not the calendar. Slide the room temperature, pick a duvet and say whether you sleep warm or cold, and see how the pairing is likely to feel.
You also get the usual bands (warm room, low tog; cold room, high tog), the commonly advised bedroom temperature, and a few things to try before buying anything new: layers, a good shake and wash, and measuring your mattress.
You're lying under the duvet, and it's either a sauna or a damp tent. Before blaming the mattress or the radiator, look at one small number on the duvet's label: the tog. It tells you how warm the duvet is meant to keep you, and the right one depends on how warm your bedroom is, which changes a lot between July and January.
What a tog actually is
A tog is a unit of thermal resistance: how hard it is for your body heat to get out through the duvet. A higher number means more warmth. It does not mean heavier or thicker, because some light, fluffy fillings are warmer than heavy ones. That's why you can't judge a duvet by squeezing it in a shop.
In most of Europe, duvets are sold by tog or by a simple 1 to 4 warmth scale, and the scale differs by brand. If a label only shows a scale, look for the tog value in the product details, or ask which tog it matches.
Try it: slide the room temperature
Set your bedroom's night temperature, pick a duvet, and say how you usually sleep. The bar shows how the pairing is likely to feel. It's a simple rule of thumb, not a measurement, so treat the answer as a starting point.
The rule of thumb
Most tog guides land in the same place. The exact cut-offs vary a little from shop to shop, so read these as bands, not walls.
| Bedroom at night | Duvet that usually suits |
|---|---|
| Warmer than about 18 °C | Around 4.5 tog (summer weight) |
| About 15 to 18 °C | Around 10.5 tog |
| Cooler than about 15 °C | Around 12 to 13.5 tog (winter weight) |
Then adjust for the person. Warm sleepers often stay comfortable under a 4.5 tog duvet even when the room is cool, and cold sleepers tend to want 10.5 tog or more. Slide the "I usually sleep" box in the planner above and you'll see the same shift.
What temperature should the bedroom be?
Health services that give sleep advice commonly suggest a bedroom of around 16 to 18 °C, and note that a cooler room helps you drop off. Plenty of people keep it warmer than they need to. If your bedroom sits well above that, try the heating a degree or two lower before buying a thicker duvet. If it sits well below, your bedroom may be better served by a draught strip on the door or a thick curtain than by more togs.
Before you buy a new duvet
Cosy isn't about owning more. A few things to try first:
- Layer instead of replace. A throw or bedspread on top of the duvet adds warmth on the coldest nights, and comes off in spring. One duvet plus a layer can cover most of the year.
- Look at the duvet you have. A flat, lumpy duvet loses warmth. A good shake each morning, and a wash according to the care label, brings a lot of it back.
- Share smartly. If you and a partner disagree, two single duvets on one bed settle it without a negotiation.
- Consider an all-seasons duvet. These are two layers, a light one and a medium one, that you can use separately or clip together. It is one purchase instead of two, though they are bulkier to store.
If you do shop, a duvet is a bulky item to return, so a few minutes of checking up front helps.
Measure before you buy
Duvet and cover sizes are not the same across Europe, so a "double" from one shop may not match a "double" from another. Measure your mattress width and length with a tape, then compare them with the duvet's stated size in centimetres, not just the name. Check the cover size too, because a duvet in a cover that is too small bunches up and loses its warmth in the corners. Also measure the space where you plan to store the spare duvet. A winter duvet takes up more room than you'd think, and a vacuum storage bag helps.
A note on babies
Babies under one year shouldn't sleep under a duvet. Follow the safe-sleep advice from your own health service for the youngest children, and keep to lower togs for toddlers and children.
The short version
Choose the tog to fit the bedroom, not the season on the calendar. Warm room, low tog. Cold room, high tog, and add a layer for the coldest nights. Measure your mattress before you buy anything, and try a throw or a shake-and-wash before you spend anything.