A super king mattress measures 203 × 203 cm and a king measures 183 × 203 cm, so a super king is 20 cm wider and exactly the same length. Shared by two people, that is roughly 101 cm each on a super king against 91 cm on a king. The trade-off is floor space, frames and bedding.
- If your bedroom wall is under about 3.3 m: pick a king, such as the Cradle Rest 5 Zone Pocket Spring Mattress, so you keep walking space on both sides.
- If a restless partner, a child or the dog shares the bed: pick a super king like the Posture Delight Pocket Spring Mattress, which is made in both sizes and rated Firm, 7 out of 10.
- If you go super king, size the bedding too: the Waterproof Mattress Protector comes in a 203 × 203 cm super king size, fitted 40 cm deep.
In this guide
What the extra 20 cm actually changes
Because both sizes are 203 cm long, a super king is not a "bigger bed" in every direction. It is a king with 20 cm added to the width, which turns the mattress into a perfect square. Tall sleepers gain nothing from moving up, because neither size is longer than the other. What changes is how much side-to-side room each person has, and how much of the bedroom the bed takes up.
Split down the middle, the extra 20 cm is about 10 cm more for each sleeper: small on paper, but often the difference between an elbow landing on your partner or on the mattress. For context, a queen is 153 cm wide, so a king is 30 cm wider than a queen and a super king is 50 cm wider.
| Feature | King | Super king |
|---|---|---|
| Mattress size (W × L) | 183 × 203 cm | 203 × 203 cm |
| Shape | Rectangle, 20 cm longer than it is wide | Square |
| Width each, for two sleepers | About 91 cm | About 101 cm |
| Wall width for the mattress plus 60 cm each side | 303 cm, plus the frame | 323 cm, plus the frame |
| Fitted sheet | King | Super king only; king sheets will not stretch to fit |
Pieces in this guide
Will a super king fit your bedroom?
Room size decides this more often than comfort does. Our showroom rule of thumb is to leave at least 60 cm of walking space on each side of the bed and at the foot, so you can get in and out, make the bed and open wardrobe doors without squeezing past. Add the width of the bed frame and any bedside tables on top of that.
Do the sums for your own room before you shop:
- Measure the wall the bedhead will sit against, wall to wall, and note where windows, power points and doors fall.
- Add up what has to fit along it: the mattress width (183 or 203 cm), the extra the frame adds, two bedside tables, and 60 cm of walking space each side if both sides are used.
- Mark the footprint on the floor with masking tape at both widths. Walk around it, open the wardrobe and the door, and see which one still feels like a room.
- Check the foot of the bed against dressers, a TV unit or the doorway swing. Both sizes are the same length, so this does not change between them.
If the taped-out super king leaves you edging sideways past a wardrobe, a king is the better call. The extra width only helps if the rest of the room still works.
Who a king suits, and who needs a super king
A king suits most couples
For most couples moving up from a queen, a king is the comfortable middle ground: 30 cm more width without taking over the room, and king bedding and frames are usually easier to find. If you sleep fairly still and the bedroom is on the snug side, a king is the sensible choice.
A super king suits restless sleepers and shared beds
The case for a super king is about distance. When two people share a bed, every roll, kick and early alarm travels across the mattress. More width puts more distance between you, so less of your partner's movement reaches your side. Pair that with a pocket spring mattress, where individually wrapped springs move on their own rather than as one connected unit, and you limit the disturbance from both directions. Our guide to how pocket spring mattresses work explains why.
A super king also makes sense when the bed regularly holds more than two: a toddler who arrives at 2 am, or a dog that has claimed the foot of the bed. And solo sleepers who like to sprawl diagonally are allowed one too. There is no rule that says a super king is only for couples.
Size and firmness are separate decisions
A bigger mattress is not a firmer one. Firmness is a feel, set by the spring gauge and the comfort layers. We group our mattresses into four collections, Soft & Plush, Medium Firm, Firm and Extra Firm, and each product page also gives the mattress its own feel label and a score out of 10. Side sleepers usually lean towards Soft & Plush or Medium Firm, back sleepers towards Medium Firm (or Firm for heavier builds), stomach sleepers towards Firm, and couples often meet in the middle at Medium Firm. Our sleeping positions and firmness guide goes into more detail.
King and super king mattresses in our range
Browse every super king mattress and every king mattress online, or see current offers in the mattress sale. Our three super king picks in this guide all sit at the firmer end.
Super king options
The Posture Delight Pocket Spring Mattress is the all-rounder. It has a 20 cm pocket spring core in a firmer 2.3 mm wire under a 5 cm comfort foam layer and convoluted foam quilting, for a 28 cm mattress that its product page labels Firm, 7 out of 10. It is made in all six sizes, from Single to Super King, so it also works if you are still deciding between king and super king.
The SleepMaker Cocoon Silver Firm is built on SleepMaker's SensorZone® pocket spring system, with a breathable Climatex® quilt and temperature-reactive KülKōte on top and a solid Comfort:Edge foam surround that supports the mattress right to its sides. It has a firm feel of about 8 out of 10, stands 29 cm tall and arrives as a conventional, uncompressed mattress.
The third is the Firm Core Mattress with Coconut Fibre, for people who want a very firm bed. It is a Bonnell spring mattress, with interconnected springs, a coconut fibre board, a high-density foam layer and a bamboo fabric cover.
Extra choice in king
If you want a softer or zoned feel, the king size opens up more options. The Supreme Care 5 Zone Memory Foam Mattress is a pocket spring mattress, not an all-foam one: a 25 cm, five-zone pocket spring core with reinforced edge rows sits under a memory foam quilted top, for a 30 cm height and a feel its page labels Plush, 4 out of 10. The Cradle Rest 5 Zone Pocket Spring Mattress also has a 25 cm five-zone pocket spring core, with a plush quilted top and a feel labelled Medium, 5 out of 10. The Spine Care 5 Zone Pocket Spring Mattress is a 26 cm five-zone option, also labelled Medium, 5 out of 10.
For a spare room, the slim 20 cm Sleep Essential III Pocket Spring Mattress is soft, and the Sleep Vital Pillow Top Mattress, Deluxe Sleep Bonnell Spring Mattress and Sleep Essence Bonnell Spring Mattress are soft Bonnell spring builds. None of these comes in super king.
Feel is personal, so lie on both sizes before you decide. We have five showrooms (Rocklea, Virginia, North Ipswich, Bundall and Beenleigh); ask which store has the mattress you like on display.
Bed frames, bedding and getting it inside
Changing size means changing everything that touches the mattress. Budget for these before you commit:
- Bed frame or base. A super king needs a super king frame; it will not sit properly on a king base. Use a solid platform base or a slatted base with evenly spaced slats, which is what our mattress product pages recommend.
- Fitted sheets. A king fitted sheet is cut for a 183 cm wide mattress and will not stretch to 203 cm. Buy super king sheets, and check the pocket depth suits the mattress height.
- Quilt and cover. A king quilt on a super king will hang short at the sides. Match the quilt and cover to the bed.
- Mattress protector. Buy it in the same size as the mattress so it fits snugly.
Think about access too. A king mattress can be stood on its 183 cm side to clear a low ceiling or a tight landing. A super king is square, so whichever way you turn it, it is 203 cm. If your home has a narrow staircase or a tight turn into the bedroom, measure first and read our guide on how to get a mattress up stairs before you choose.
King vs super king FAQs
What size is a super king mattress in cm?
A super king mattress is 203 cm wide and 203 cm long, which makes it square. A king is 183 cm wide and 203 cm long.
Is a super king bigger than a king?
Yes, but only in width. A super king is 20 cm wider than a king, which works out to about 10 cm more for each person when two people share the bed.
Is a super king longer than a king?
No. Both are 203 cm long, so a super king gives tall sleepers no extra length. If length is the issue, moving from a king to a super king will not change it.
Can you use king sheets on a super king mattress?
Not fitted sheets. A king fitted sheet is made for a 183 cm wide mattress and will not stretch over a 203 cm super king. Use super king fitted sheets, and match the quilt cover and mattress protector to the bed as well.
Is a super king worth it if you sleep alone?
It can be, if your bedroom has the space and you like to spread out. The extra width is just as useful to one person who sleeps diagonally as it is to a couple. If the room is tight, a king or queen will leave you more floor space.
Does a bigger mattress feel firmer?
No. Firmness is a feel set by the spring gauge and the comfort layers, not by the size of the mattress. Choose the size for your room and the feel for the way you sleep, as two separate decisions.