Down vs Synthetic Duvet: Which Tog Feels Warmer?

Aug 24, 2026 / Oct 5, 2026 · 6 min read · togs bedding uk duvet tog-rating down-duvet synthetic-duvet hollowfibre duvet-comparison winter-duvet ·

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The tog is the same; the duvet is not

Which? tested 24 duvets with a panel of 40 testers and found that "the best synthetic duvets in our test scored just as highly for comfort as feather and down options, and in some cases surpassed them." So the answer to "which feels warmer, down or synthetic?" is not as simple as the price tag suggests. At the same tog rating, the difference you feel in bed is mostly weight, feel, care and lifespan.

This guide explains what the tog does and does not measure, how the two fillings differ according to Which? and UK retailers, and what that means for your choice.

What the tog measures, and what it doesn't

A tog measures thermal resistance: how well a duvet slows the loss of heat. According to Wikipedia, one tog equals 0.1 square metre kelvin per watt, measured under the British Standard BS 4745. The rating tells you about warmth, whatever the filling.

It does not tell you about weight. Argos calls it "one popular misconception" that tog ratings "relate to the weight of the duvet", and explains that weight and thickness are "determined by the filling inside." Marks & Spencer puts it plainly: "Weight and thickness don't have a direct correlation – a thin duvet can have a higher tog rating depending on the filling."

One more caution. Wikipedia notes that the tog printed on British duvets is "a minimum; actual values may be up to 3 tog higher." Two duvets with the same label, one down and one synthetic, are not guaranteed to be equally warm.

Why synthetic feels heavier

The main practical difference is weight. Primark explains that "synthetic fillings often require more material to match the insulation of a down duvet. This results in heavier duvets with the same tog rating as lighter, natural-filled ones. In short, thicker doesn't always mean warmer."

So at the same tog, a synthetic duvet usually weighs more. Some sleepers like that settled, heavy feel; others find it oppressive. Which? splits its comfort results between people who prefer a light duvet and those who prefer a heavy one, which shows how much this preference matters.

The two fillings compared

Which?'s guide sets out the trade-offs:

	Synthetic (hollowfibre)	Feather and down
Price	"Sometimes cheaper"	"Can be more expensive than synthetic"
Washing	Machine washable	Most can be washed at home at 40°C or 60°C, but harder to dry
Lifespan	"Typically last up to five years"	"Last longer than synthetics if cared for properly"
Allergies	Some are hypoallergenic	Not for people allergic to feathers
Weakness	Filling "can clump together"	Harder to dry properly

Which? also describes microfibre as a newer synthetic "designed to be a synthetic equivalent to down", and "one of the lightest and most supple" fillings. If you want the light feel of down without the feathers, microfibre is the synthetic to look at.

Beyond down and synthetic: wool and silk

Which? also covers two less common fillings. Wool is "similarly priced to feathers and down but has the advantage of being naturally hypoallergenic and dust-mite resistant," and it is "renewable, sustainable and biodegradable." Its drawbacks: it can be expensive, needs washing "gently at a low temperature", and "can seem flat compared with other fillings." Silk is "naturally hypoallergenic and resistant to dust mites", keeps you warm "while preventing overheating", but is expensive and needs professional laundering.

Where the fillings come from

Makers describe their fillings differently. Slumberdown, for example, says its synthetic fillings are "easy to care for, lightweight, non-allergenic", and that "a high proportion of these fillings are made from recycled plastic bottles." Its natural fillings are "all feather or a mix of feather and down, either from duck or goose," and it says "all our natural products are ethically sourced and fully certified." Check each product page for the filling's make-up; the ratio of feather to down affects both warmth and price, as Which? notes.

Allergies: hypoallergenic or anti-allergy?

If allergies are part of the decision, Which? draws a distinction worth knowing. "Hypoallergenic" means the filling is not made of known allergens "such as feathers or wool", but "dust mites, can still develop." "Anti-allergy" means "the filling and casing will have been treated to resist and combat the development of dust mites," which may suit people with "asthma, eczema or rhinitis." Whatever you choose, Which? says dust mites are killed "by washing at temperatures of 60°C or above."

What the price difference looks like

The gap between the two fillings is clear on UK retailers' own listings. These were the lowest listed prices for a 10.5 tog duvet when we checked on 5 October 2026:

Retailer	Synthetic 10.5 tog	Natural 10.5 tog
Dunelm	Fogarty Warm & Cosy, from £16	Fogarty Duck Feather and Down, from £55
John Lewis	Synthetic Soft Touch Washable, from £30	Natural Duck Feather and Down, from £50; Hungarian Goose Down, from £200

At the budget end, natural filling costs roughly two to three times as much at the same tog. Goose down costs several times more again.

Over the years

Lifespan changes the sums. Which? puts a synthetic duvet's typical life at "up to five years", while feather and down last longer with care. Over a decade, one good feather and down duvet may cost no more than two cheap synthetics. Silentnight recommends washing a duvet "every 6-12 months", and Which? "once or twice a year"; a synthetic is the easier of the two to wash at home.

All-seasons sets in either filling

Both fillings come as all-seasons sets. Which? describes the usual set as "one light duvet (usually about 4.5 tog) and one heavier one (usually about 9 tog)", used separately in summer and spring or autumn, and combined in winter. It says these sets "often cost a bit more upfront" but are "usually cheaper than buying separate summer and winter duvets." John Lewis, for example, sells them in synthetic, duck down and goose down.

Which to choose

Light and long-lasting: feather and down, or goose down if your budget allows.
Allergies or frequent washing: synthetic, ideally labelled anti-allergy and washable at 60°C.
Light feel without feathers: microfibre.
Lowest price: synthetic, from about £16 at Dunelm.
Comfort: either. Which? found the best synthetics matched feather and down.

Choose the tog for your bedroom first, then the filling. Our tog rating chart by season covers the tog, and how tog ratings are measured explains the test.

Where to buy

Both Dunelm and John Lewis let you filter duvets by tog and filling, which makes a like-for-like comparison easy. For reviews of specific ranges, see our Dunelm duvet review, Silentnight vs Slumberdown and White Company vs John Lewis.