Duvet weight and layering

Match your duvet's warmth (tog) to the season, and use layers so you can adjust through the night. Weighted blankets have some evidence, but mainly in people with psychiatric conditions.

• Evidence: Weak
• Low effort
• Medium cost
• Works: tonight

Why it matters

Overheating under the covers is one of the easier sleep problems to fix. With bedding on, heat exposure increases wake-ups and reduces deep sleep and REM, and humid heat is worse [5]. When sleep is going well, the air between you and the covers usually sits around 32–34°C (90–93°F) [5]. Your duvet is the main thing that sets it.

The right duvet depends on your room, your body and the season, so one duvet rarely works all year.

How to do it

1. Read the tog. Tog measures how well something insulates: the higher the number, the warmer [1][2]. In the UK, the British Standard BS 5335 covers continental quilts, including how their thermal resistance is measured [3].

2. Pick by season. Guidance from the UK consumer group Which? and the textile lab IDFL [1][2]:

   Season	Tog	Source
   Summer	1–4.5	Which? says 1–4 (and the light half of a four-season set is about 4.5); IDFL says 4–5
   Spring and autumn	6–10.5	IDFL
   Winter	10.5–15	Which?; most people find 13.5 enough for a British winter

   Adjust for your bedroom. A cool, unheated room in winter needs the top of the range; a warm, centrally heated flat may need less. See room temperature.

3. No tog on the label (common in the US)? Down comforters list fill power: how much space a set weight of down fills, in cubic inches. Higher fill power means better down, which gives more warmth for the same weight [4]. But fill power isn’t warmth. Total warmth depends on fill power and on how much down is inside [4], so check the fill weight too. If neither is listed, compare a seller’s own “light”, “all-season” and “warm” options.

4. Consider a four-season set. These come as two duvets, usually about 4.5 and 9 tog, that you use separately or clip together in winter [1].

5. Layer to fine-tune. Two thinner layers beat one thick one, because you can push one off at 3 a.m. without waking fully. A light blanket on top of a summer duvet covers most of spring and autumn.

6. Couples who disagree: use two single duvets of different togs on one bed. See sharing a bed.

7. Pick the fill and cover for how you sleep. Fibre matters less than tog, but cover fabric affects breathability. See bedding materials.

Weighted blankets

In a trial of 120 adults with depression, bipolar disorder, anxiety or ADHD, people given an 8 kg (17.6 lb) chain blanket had much less insomnia after 4 weeks than people given a light 1.5 kg (3.4 lb) one. Ten people found 8 kg too heavy and switched to 6 kg (13.2 lb) [6]. Two 2024 meta-analyses of 8 and 9 studies, all in people with psychiatric conditions, found weighted blankets reduced anxiety. For insomnia, the results were mixed, and many studies were small or at high risk of bias [7][8]. No serious side effects were reported [8].

If you’re a healthy sleeper, there’s little evidence either way. A heavy blanket is also an extra layer, so hot sleepers may find it too warm. Never use a weighted blanket for a baby: the US Consumer Product Safety Commission says not to use weighted blankets or swaddles for infants [9]. If you have a breathing, heart or circulation condition, or can’t easily move the blanket off yourself, ask your doctor before trying one.

Common mistakes

• Using a winter duvet all year. If you wake hot in spring, swap down a level.
• Comparing fill power across different products as if it were warmth. A high fill power comforter with little down can be cooler than a lower fill power one with more [4].
• Fixing a hot bedroom with a thinner duvet only. Cool the room as well.

Effect on your sleep score

We found no study measuring duvet tog with wearables.

• Wake-ups, deep sleep and REM: a duvet that’s too warm can cost you all three, through heat [5]. Getting the warmth right mostly prevents losses rather than adding gains.
• Weighted blankets: in the 2020 trial, actigraphy (a wrist-worn movement sensor) showed better sleep maintenance with the weighted blanket [6]. That was in psychiatric patients.

How confident: low for duvets in healthy people; moderate that overheating hurts sleep.

Evidence

Rated Weak. The link between heat and broken sleep is well described [5], but the tog ranges come from consumer and testing-lab guidance, not from sleep trials [1][2]. For weighted blankets, the best trial is good quality but was done in psychiatric patients, and participants could feel which blanket they had [6]. Both 2024 reviews call for larger, better trials [7][8].

General information for healthy adults, not medical advice. If you have a sleep problem that lasts, read when to see a doctor. Sources checked 4 October 2026. Spot a mistake? Tell us.