Mattress Topper Size & Depth Guide
A good bed can fix your bad day, but on the other hand, a bad one can make your nights uncomfortable and long. In the UK, many people turn to our mattress topper size guide to choose bed toppers to get an improved feel at their beds without spending many on a brand new mattress.
This is the easiest upgrade you can make for better sleep, but only if you choose the right size and thickness. A poorly fitted topper can slide around, fold at the corners, or feel uneven under your sheets, which just ruins the whole point of adding it in the first place.
At MightySoft, mattress toppers are designed to fit UK beds properly while adding real comfort and support. With options across all standard UK sizes, MightySoft toppers bring balance to your sleep surface. This guide breaks down UK mattress topper sizes and depths in a clear, practical way, helping you choose a topper that fits your bed and your sheets.
Why Mattress Topper Size Is More Than Just a Number?
The following is what proper sizing means:
- It stays in place better
- Your fitted sheet actually fits without snapping off corners
- You get full support across the whole bed
- It looks neat, and your sleep surface feels intentional, not chaotic
UK bed sizing follows its own standards, so you shouldn’t rely on international labels like "Queen," which is not a standard UK size.
UK Mattress Topper Sizes (Width × Length)
Single (90 × 190 cm)
The Single topper is the most common choice for solo sleepers, kids, teens, and guest room beds. Because it’s lighter, it’s easier to lift when changing sheets or cleaning.
If your mattress is still fairly new but feels a little firm, a slim 5 cm single topper gives a small comfort boost without changing the mattress feel too much.
If the mattress is old or uneven, a deeper 7.5 to 10 cm topper will mask sagging better and make the surface feel smoother.
Small Double (120 × 190 cm)
The Small Double is a uniquely UK size. It is great if you want more room than a single bed, but don’t have the space (or budget) for a full double.
It works for couples who don’t mind a cozier sleep setup, or solo sleepers who like extra room to roll around.
A medium 7.5 cm topper in this size gives noticeable shoulder and hip cushioning for side sleepers. A deeper 10 cm topper can make an old, small double mattress feel significantly more luxurious and supportive.
Double (135 × 190 cm)
The Double topper is the standard choice for most UK couples. It balances comfort and space well, and sheets are easier to manage compared to bigger beds.
If you share your bed with someone who moves a lot at night, a 7.5–10 cm memory foam or latex topper helps reduce motion disturbance a bit better than thinner options.
A 7.5 cm softens nicely, in case your mattress feels firm. And if your mattress is sagging or uncomfortable, then a 10 cm or more will be helpful.
King Size (150 × 200 cm)
A King Size topper is brilliant for couples who want more personal space without upgrading to the giant Super King. If you’re taller, the extra 10 cm length compared to a double bed stops you from sleeping diagonally just to avoid your feet hanging off.
A 7.5 cm king topper gives balanced comfort for most sleep styles.
A 10 cm king topper provides deep pressure relief for sore backs, shoulders, and hips. Sometimes, couples choose two single toppers sideways on a king mattress in order to get firmness on every side.
Super King (180 × 200 cm)
This is the biggest standard UK topper size. If you want that “luxury hotel bed” feel, or if you and your partner sleep like you’re claiming separate territories, Super King gives you all the room you need.
A deeper topper (10 cm or more) makes this bed feel cloud-like, smooth, and extremely pressure-relieving.
The only downside? It makes sheet-changing feel like a gym workout, and sometimes you need extra-deep sheets depending on your mattress height. But honestly, the comfort is worth the struggle.
Mattress Topper Depths in the UK
5 cm (2 inches) - Slim Topper
This is the thinnest standard topper depth in the UK. It works well if:
- Your mattress is still in decent shape, just slightly firm
- You want a light layer of cushioning without sinking in
- You’re a stomach sleeper and need minimal loft
- You want a bed that doesn’t feel too tall when layering different bedding parts
A 5 cm topper adds comfort but won’t hide major mattress sagging or dips. It’s more like a “comfort tweak” than a transformation.
7.5 cm (3 inches) - Medium Depth Topper
This is the most balanced and popular thickness because it provides:
- Clear cushioning under the shoulders and hips
- Better spine alignment for side and back sleepers
- More pressure relief than 5 cm without feeling “too stuck.”
- A noticeable comfort upgrade for most sleepers
- It’s the Goldilocks depth for many UK sleepers.
10 cm (4 inches) - Deep/Plush Topper
Choose this if:
- When your mattress gets uneven, old, or sagging
- If you are struggling with pressure pains in areas like the lower back, shoulders, and hips.
- You want your bed to feel much softer or more luxurious
- You’re a back or side sleeper needing deeper support
A 10 cm topper dramatically changes the feel of your bed and clearly shows how mattress toppers work to transform comfort. It can make a very firm or worn mattress feel almost new. But it might feel too sinking for stomach sleepers or those who prefer a firmer surface.
How Topper Size and Depth Impact Different Sleep Needs?
For Back Pain
A topper must match your mattress size perfectly so it doesn’t move. Thickness should be at least 7.5 to 10 cm for better pressure relief and spine support. Slim toppers may soften a mattress, but they won’t provide enough spinal support if pain comes from pressure points or sagging.
For Side Sleepers
Cushioning under the shoulders and hips is key. Medium to deep toppers (7.5–10 cm) help avoid numb arms, sore shoulders, and hip pressure. A king or super king size works best for couples needing more space.
For Old or Sagging Mattresses
King or Super King if the bed is large. Depth should be 7.5 to 10 cm or more to mask unevenness. Deep toppers can smooth out dips and improve pressure relief significantly.
Common Mistakes When Choosing a Mattress Topper
- Not measuring the mattress first, as outlined in this mattress topper size guide
- Assuming UK and US sizes are the same
- Choosing a topper too thick for your sleep style
- Forgetting sheet depth needs to change with topper thickness
- Thinking toppers fix everything. They help a lot, but can’t fix a broken mattress
Conclusion
A mattress topper can act as a small change in reshaping your sleep in a huge way when the depth and size match your bed exactly. The right thickness will help support your spine, cushion the sore spots, and bring comfort as per your sleep style, not any guesswork, as explained in this mattress topper size guide.