“Choose the depth before the brand, and buy a memory foam topper only for a mattress that is firm but still flat. If you sleep hot or cannot risk a purchase you are unable to return, the cover and the trial matter more than an extra centimetre of foam.”
Check the mattress before you buy a topper
A memory foam topper changes how a mattress feels, not how it supports you. Making a firm mattress softer is the job memory foam does well, spreading load at the shoulder and hip as it warms and moulds. It will not rescue a mattress that has sagged. Bed Advice UK, the National Bed Federation’s advice site, points out that a topper laid over deep dips will quickly mould to those same dips. If your mattress has a visible hollow, compare memory foam mattresses instead; our mattress topper comparison covers fibre, feather and latex too.
Choose the depth for the job
Bed Advice UK recommends at least 5cm, because anything thinner is unlikely to make a noticeable difference, and most toppers here sit between 4 and 6.5cm. The thick memory foam toppers on this page are the 8cm Inofia Cooler Gel, also sold at 10cm in double and king, and the 10cm versions of the Dunelm Gel Fusion and the Dorma TENCEL Blend. They suit a very firm mattress and side sleepers whose shoulder needs to sink further. Extra foam also makes a topper heavier to lift, turn and fit under a sheet.
Memory foam topper depth and what it changes
| Depth |
What it changes |
Picks on this page |
| 4 to 4.5cm |
Takes the edge off a slightly firm mattress, below the 5cm Bed Advice UK recommends |
REM-Fit Halo, Soak&Sleep |
| 5cm |
The usual depth, softens a firm mattress for back and side sleepers |
Panda, TEMPUR ONE, OTTY, Brightr Aurora |
| 5.7 to 6.5cm |
More give at the shoulder and hip, heavier to lift and turn |
Dunelm Memory Foam, Dunelm Gel Fusion, Dorma TENCEL Blend |
| 8 to 10cm |
Changes the feel of a very firm mattress, needs deeper fitted sheets |
Inofia Cooler Gel, 10cm Dunelm Gel Fusion, 10cm Dorma TENCEL Blend |
How warm memory foam sleeps
Memory foam softens with body heat, which is why it contours and also why it can feel warm. In a small randomised crossover trial published in PLOS One in 2018, Chiba and colleagues compared a high-rebound polyethylene fibre topper with a 3.5cm TEMPUR memory foam topper in 30 men. In the ten younger men, core body temperature stayed 0.1 to 0.3°C higher on the memory foam between midnight and 3am, and deep-sleep delta power early in the night was 27.8% higher on the high-rebound topper. The study was sponsored by airweave, the maker of the high-rebound topper. The toppers here tackle heat in three ways, with gel particles and ventilation holes (Dunelm Gel Fusion, Inofia), open-cell foam (REM-Fit Halo, OTTY) and moisture-managing covers (Panda’s bamboo blend, Dorma’s TENCEL lyocell). These are design features, not measured results, and the plain Dunelm Memory Foam has none. If you already run hot, the NHS advice that sleep comes more easily in a room that is “quiet, dark and cool” is worth following whatever the foam, and our cooling mattress topper comparison looks beyond memory foam.
Firmness and sleeping position
A softer bed is not automatically kinder to your back. In a randomised trial of 313 adults with chronic low back pain, Kovacs and colleagues reported in The Lancet in 2003 that people given a medium-firm mattress were more likely to improve for pain in bed than those on a firm one (odds ratio 2.36). A 5cm memory foam topper on a firm mattress moves the surface in that direction, while a 10cm topper on a mattress that is already medium can let a back or front sleeper’s hips sink too far. Side sleepers can go softer and deeper, back sleepers usually suit 5cm, and front sleepers are better on the firmer side of the reversible Brightr Aurora or the 4cm REM-Fit Halo.
Covers, returns and UK sizes
Check the care line before you buy. Seven of the ten covers here go in the washing machine. The OTTY cover is dry clean only, Dunelm lists both the Dorma TENCEL Blend and its own Memory Foam topper as sponge clean, and none of the foam cores goes in the machine. A topper you have slept on usually goes back only under a sleep trial, so the trial terms count as much as the foam. The Inofia and Brightr carry 100-night trials, the Panda, TEMPUR ONE and REM-Fit 30 nights and the OTTY 14. Dunelm, which also sells the Dorma, takes back unused toppers within 28 days, Soak&Sleep within 365 days. UK beds use 90x190 for a single, 120x190 for a small double and 135x190 for a double. The Panda, REM-Fit, Brightr and Inofia come as a true small double, while the TEMPUR ONE starts at double. King and super king owners can also look at Silentnight’s Impress 5cm, made in the UK according to Silentnight and sold only in those two sizes, and our double, king size and super king topper comparisons.
Inofia and Brightr were selling below these regular prices when we checked.
