Getting the tog rating right matters for warmth, but the wrong duvet size undoes a lot of that work: a duvet that’s too narrow lets cold air in at the edges no matter how warm the filling is. Sizing is also where most of the buying mistakes happen, particularly around king-size beds, so it’s worth getting right before you invest in a warmer winter duvet.
UK Duvet Sizes at a Glance
| Duvet size | Typical bed size | Roughly fits |
|---|---|---|
| Single | Single bed | One sleeper |
| Double | Double bed | One or two sleepers, cosy fit for two |
| King | King-size bed | Two sleepers, comfortable coverage |
| Super king | Super king bed, or a king bed for extra coverage | Two sleepers who want no shared edge |
Content team: confirm exact centimetre measurements against current product specs before publishing, sizing can vary slightly by manufacturer.
The Mistake Most People Make: Buying a Double for a King Bed
It’s an easy mistake, and a common one: a double duvet looks close enough in size to a king bed that people assume it’ll do. In practice, a double duvet on a king-size bed leaves a noticeable gap at the edges, which is exactly where cold air gets in overnight. If you’ve upgraded your bed size but kept your old duvet, that mismatch is often the real reason the bed feels colder than it used to, not the tog rating.
For a full breakdown of exactly how king and super king duvets compare, including which one makes sense if you or your partner tend to pull the covers, see our king vs. super king duvet guide.
Should You Size Up to Super King?
Super king duvets aren’t only for super king beds. Plenty of people with a standard king-size bed choose a super king duvet specifically for the extra overlap it gives each sleeper, which is worth considering if:
- You or your partner tend to pull the duvet across in the night.
- One of you runs noticeably colder and wants more coverage on your side.
- You’ve previously felt a cold gap along the edge of the bed, even with the “correct” size duvet.
The trade-off is a heavier duvet and a bit more overhang, so it’s a personal preference rather than a strict upgrade. If in doubt, the king vs. super king comparison has more detail on how the two actually feel in use, not just their measurements.
Matching Your Bedding to the Right Size
Once you’ve settled on a duvet size, the rest of your bedding needs to match it, a duvet cover, sheets, and mattress protector that don’t correspond to your actual mattress and duvet size will bunch, slip, or leave gaps of their own:
- Our cotton mattress protectors are sized to match standard UK bed dimensions, worth checking alongside your duvet if you’re upgrading both.
- Percale sheets and our sateen collection are available across the same size range, so it’s worth ordering duvet, cover and sheets together rather than assuming an old cover will fit a new duvet.
- Explore the full king-size collection if you’ve confirmed king is the right size for your bed and are ready to shop.
Frequently Asked Questions
What size duvet do I need for a king-size bed?
A king duvet, not a double. A double duvet is noticeably narrower than a king-size bed and will leave gaps at the edges where cold air can get in. If you or your partner tend to pull the covers, a super king duvet on a king bed is also a common choice for extra coverage.
Is a super king duvet too big for a king-size bed?
No, it's a common and comfortable choice. A super king duvet on a king-size bed gives more overhang on each side, which many couples prefer, particularly if one person tends to pull the duvet across in the night.
How do I know if my current duvet is the wrong size?
The clearest sign is a persistent cold gap along the edge of the bed, or one partner regularly ending up with less coverage than the other. If your bed size has changed since you bought your duvet, it's worth double-checking the sizing rather than assuming it still fits.
Do single and double duvets fit different bed sizes exactly?
Broadly yes, single duvets are sized for single beds and double duvets for double beds, but always check the specific measurements on the product page against your mattress, since sizing can vary slightly between manufacturers and styles.
Should I buy my duvet size based on my mattress or my bedroom?
Always base it on your mattress size, not your bedroom. A duvet that matches your bed will keep you warm regardless of room size; a duvet chosen to 'look right' in a larger bedroom but mismatched to the bed will leave cold gaps.
Ready to shop? Browse our king-size duvet collection or read what tog duvet you need for winter to choose warmth as well as size.
