All Tog Duvets lists king as 225 × 220 cm and super king as 260 × 220 cm: 35 cm wider at the same length. Other named ranges differ, including the 230 × 220 cm Dunelm king-cover reference. Check the exact insert and cover rather than assuming one universal UK size.
Compare the extra width to scale ↓
Open bedding size converterIn this guide
Compare the extra width to scale
260 − 225 = 35 cm extra total width. Centred over the same bed, that adds 17.5 cm per side. It does not add any length.
Compare like with like in the size chart
All Tog Duvets lists these insert dimensions, and Belledorm lists matching named cover dimensions. Dunelm’s king-cover reference is 230 cm wide instead. This is a real range difference, not a conversion error: keep the publisher and item type beside the value. Read width first and length second. An imported king label may use another market’s dimensions.
| Named UK reference | Width × length | Approximate inches |
|---|---|---|
| All Tog king duvet | 225 × 220 cm | 88.6 × 86.6 in |
| All Tog super king duvet | 260 × 220 cm | 102.4 × 86.6 in |
| Dunelm king cover | 230 × 220 cm | 90.6 × 86.6 in |
| All Tog king-to-super-king difference | 35 cm wider; same listed length | 13.8 in wider |
Read the evidence: All Tog Duvets size chart · Belledorm bedding size guide · Dunelm bed linen buying guide
A side-allowance example on a king mattress
For an illustrative 150 cm wide mattress, a flat-plan king duvet allows (225 − 150) ÷ 2 = 37.5 cm at each side. Super king allows (260 − 150) ÷ 2 = 55 cm. That is 17.5 cm more on each side when centred. These calculations use the cited widths; they do not measure the duvet while someone is sleeping beneath it.
Bodies, filling loft and mattress thickness use some of the fabric. A wall, low frame or nearby floor can also change whether the extra drape is useful. Measure the bed arrangement and preferred coverage before buying.
Read the evidence: Belledorm bedding size guide
Match the cover to the insert you choose
If you put a super king duvet on a king bed, compare a cover intended for that super king insert. The mattress does not determine the cover’s width. Check the insert’s actual dimensions, the cover’s specification and the maker’s intended pairing, including internal ties and closure. Do not rely on a universal rule to buy a smaller cover for extra loft.
Read the evidence: The Company Store T-Shirt Soft Jersey Knit Duvet Cover Set
Check the care route before choosing a larger duvet
Before choosing a wider duvet, check its own care label, dry weight and the approved loading arrangement for washing and drying. More bed coverage is a separate decision from whether your home equipment can clean the replacement.
Read the evidence: Samsung UK washing cycles
Questions about fit and measurements
Can I use a super king duvet on a king bed?
You can compare that arrangement using actual dimensions and your preferred coverage. The extra width may be useful, but check drape, floor clearance, the matching cover and the care route. The size name alone does not establish a good fit.
Is a US king duvet the same as a UK super king?
Do not equate the names. Check the insert and cover dimensions from the selected ranges in the same units. US comforter and cover ranges can combine sizes or use different dimensions.
Sources and scope
- All Tog Duvets size chart
- Belledorm bedding size guide
- Dunelm bed linen buying guide
- The Company Store T-Shirt Soft Jersey Knit Duvet Cover Set
- Samsung UK washing cycles
Dimensions describe the named market and product range, not universal fit. Compare your exact item measurements and the manufacturer’s intended fit range before buying. Report a correction with the page and supporting source.