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Duvet Insert vs Comforter: Weight, Tog, and Fill
Tog is warmth. Fill weight is mass. Fill power is loft per ounce. A 10.5 tog down insert might be 500–700 g; a “all-season” comforter might be 40–55 oz of polyester and sleep damper.
Updated 27 Aug 2026 · 6 min read · duvet insert vs comforter weight
Three numbers that are not synonyms
Tog: thermal resistance of the whole insert. Fill power: cubic inches per ounce of down (600, 700, 800). Fill weight: grams or ounces of fill in that size. High fill power + modest weight = warm and light. Low fill power + high weight = warm and bulky. Polyester has no fill power; it has grams and marketing.
A 13.5 tog winter down king can still weigh less than a cheap polyester comforter that sleeps like a wet coat. That is the winter tog lesson in mass form.
| Object (typical queen/double) | Fill mass | Warmth language |
|---|---|---|
| Down insert, 4.5 tog, 700 fill | 250–400 g | Summer |
| Down insert, 10.5 tog, 700 fill | 500–800 g | All-season room |
| Down insert, 13.5 tog, 700 fill | 800–1100 g | Winter |
| Poly comforter “all-season” | 40–55 oz / 1.1–1.6 kg | One warmth, sewn shut |
| Wool insert, 10.5 tog | Often 1.5–2.5 kg | Heavier, damp-tolerant |
Which spec to trust on the bag
UK: tog printed, fill named, tog tested. US down: fill power and weight, 300-count down-proof cotton. US polyester comforter: weight in oz plus “light / all-season / extra warmth.” If the only number is thread count, you are in the thread-count aisle by mistake. Construction still decides whether you wash a cover or a 1.5 kg lump — how to wash a duvet.
Buy the system, not the heavier object
Insert + two covers + a tog you can live with (or a 4.5+9.0 pair) is the adult bed. A 55 oz comforter is the guest-room or the $50 whole-top-of-bed. Weight in the hand at the shop is not warmth in January.
Questions, answered
- Is a heavier duvet always warmer?
- No. 800-fill down is warmer per gram than 500-fill, and both beat polyester gram-for-gram on dry warmth. Tog is the comparison when you have it.
- Why does my 10.5 tog feel heavier than the label?
- Polyester fill, a thick sateen cover, or a damp insert. Dry it; then weigh the cover separately in your head.
- Can I use a comforter as a duvet insert?
- Only if it fits the cover and you tie it. Most comforters are too puffy and already decorative. You then have two faces fighting.
