Memory foam and microfibre are not two grades of the same thing. One redistributes your weight, the other adds padding. So the right choice depends on what is actually wrong with your bed. If your hips and shoulders ache on a mattress that is too hard, memory foam does something microfibre cannot. If the mattress is still sound but flat and unwelcoming, a deep microfibre fill gives you more of that soft hotel-bed feel, washes at home, and will not cook you in July.
That is the decision in one paragraph. The rest is the detail most comparisons skip: which one you can genuinely launder, how each one fails, and what each does to the height of your bed.
What is the actual difference between them?
Memory foam is viscoelastic polyurethane. It is a solid slab that softens where your body heat reaches it and flows away from the points you press hardest, so your weight gets carried across a wider area instead of concentrating on a hip bone. Nothing else in bedding does that.
Microfibre is a fill, not a slab. Very fine polyester filaments are blown into a quilted shell, usually held in place by box stitching. It works by loft. You compress it, air moves out, and you end up sitting on a thicker and springier cushion than you had before. It does not contour around your shoulder. It simply puts more padding underneath it.
Every answer below follows from that one distinction. Foam changes support. Fibre changes padding.
Which one sleeps cooler?
Microfibre, in most cases, and for structural reasons rather than marketing ones. Solid foam is an insulator, and warm damp air has nowhere to escape to, so heat builds up in the layer between you and it. An open fibre fill held by box stitching lets air pass through, and a cotton-blend top sheet carries moisture away rather than trapping it against your skin.
Covers and foam formulations shift this at the margins, not fundamentally. The bigger lever is how much solid foam you lie on. A 4cm layer under a breathable cover behaves very differently from a 10cm slab of the same material. Our Cooling Mattress Topper: What Actually Works (UK Guide) goes through the physics properly.
One rule reversal catches people out. For comfort, deeper usually feels better. For heat, deeper foam is worse. If you want both height and a surface that stays cool, take the height from fibre and keep the solid foam shallow.
Which is better for back, hip and shoulder pain?
Memory foam is the one that changes how your weight is carried, and side sleepers with sore hips and shoulders tend to notice the difference most. Back and front sleepers often prefer less of it, because sinking in at the waist is not helpful when your spine is already supported.
What we will not tell you is that a topper treats anything. It changes the surface you lie on, and that is the whole of its job. It cannot rescue a mattress that has lost its support: if yours dips more than about 3cm when you press down on it, you need a mattress, not a topper. Pain that persists is a conversation for your GP or a physiotherapist, not a bedding purchase.
If the real complaint is just that the bed is unforgivingly hard, fibre can solve that perfectly well, and more cheaply in terms of how much thickness you get.
Which is better for softening a firm mattress?
Both work, by different means. Fibre is the blunter instrument and often the more satisfying one, because thickness is cheap in fibre and expensive in foam. Our Mattress Topper 10cm Extra Thick, Hotel Quality is a deep microfibre fill in a cotton-blend cover with box stitching to stop the filling drifting to the edges, which is the usual failure mode of cheap fibre toppers.
Foam softens the first few centimetres of contact, then you settle onto something that still has the firmness of the mattress beneath it. That is fine if your issue is pressure points. It is less convincing if you simply want the bed to feel plusher. Our Memory Foam Mattress Topper 4cm with Cooling Bamboo Cover sits at 4cm with a zip-off bamboo-blend cover and an anti-slip base, which is the sensible depth for foam if heat is on your mind.
Can you wash a memory foam mattress topper?
No, and this is the biggest practical difference between the two. Foam must never go into a washing machine or a tumble dryer. Water sits inside the cell structure and will not come out, the weight of a soaked slab tears it apart in the drum, and dryer heat degrades it. What you can wash is the cover, if it unzips. The foam itself gets spot cleaning, airing and a vacuum.
Microfibre goes in the machine whole. Ours is machine washable and safe to tumble dry, and the fill fluffs back to full height afterwards, which is exactly what you want from a product that will absorb months of skin cells and sweat.
Our own blog is not consistent on tumble drying, so here is the rule worth keeping. Memory foam: never. Fibre and microfibre fills: yes, on low, and dryer balls help break up clumps. Waterproof protectors: low heat only. The Mattress Topper Cleaning Guide covers technique in more detail.
Why this matters beyond convenience: laundering is mostly a mechanical process, not a thermal one. In a controlled study of machine washing, water or detergent alone removed roughly 84% of the dust mite allergen Der f 1, rising to about 98% with detergent and bleach, at warm and cold temperatures alike (Arlian, Vyszenski-Moher and Morgan, Journal of Allergy and Clinical Immunology, 2003, volume 111, pages 1269 to 1273). A topper you can put in the machine therefore stays measurably cleaner than one you can only spot clean. That is a hygiene point rather than a health claim. A Cochrane review of randomised trials of house dust mite reduction measures found no clear benefit for allergy symptoms or medication use, so cleaner bedding is worth having on its own terms and nothing more.
Which one lasts longer?
Both wear out, by different routes, and neither is immortal.
High-density foam loses its rebound gradually. It stops springing back where you lie, and the dent stays in the morning. Nothing you do restores it. Fibre loses loft instead: the filaments compress and tangle, and you see shallow dips at hip and shoulder height. The useful difference is recovery, because a wash and a low tumble puts a fair amount of that loft back. Foam has no equivalent.
Two things shorten foam's life unnecessarily. Long-term vacuum packing damages it, whatever you read elsewhere on this blog, so unroll a new one and let it recover its shape rather than storing it squashed. And folding a foam slab in half repeatedly creases the cell structure along the fold, which is not somewhere you want a permanent weak line.
Which is better for allergies?
You will see microfibre sold as hypoallergenic and various fills described as mite resistant. Treat all of it carefully. Dust mites need warmth, humidity and shed skin, none of which is unique to a particular fibre, and a sealed foam slab is not a hospitable place for them but also cannot be washed if something does get into the cover.
The defensible position is the boring one: the topper you can launder regularly is the one that stays cleanest, which points at microfibre. If the real concern is spills, accidents or barrier protection, that is a protector's job rather than a topper's, and our Waterproof Mattress Protector: UK Buyer's and Care Guide sets out what the evidence does and does not support.
How thick should each one be?
The two materials are measured on different scales, which is why thickness advice online contradicts itself so often. For memory foam, around 4cm is the useful working depth for most people: thinner than that and you barely feel it, much deeper and heat retention and bed height start to cost you more than the extra contouring gains. For fibre, you need considerably more loft to make a difference, and 7cm to 10cm is where a microfibre topper genuinely changes how the bed feels.
So a 10cm fibre topper and a 10cm foam topper are not comparable products at all. For how far the thickness argument can be pushed, see What is the Thickest Mattress Topper? Your Guide to Maximum Comfort in the UK, and for how fibre density is actually specified, What Is GSM in Mattress Topper? explains the GSM figure on the label.
What about the height of the bed and your sheets?
A deep fibre topper adds real height, and that is the practical consequence people forget until their fitted sheet pings off a corner at two in the morning. Measure your mattress, add the topper depth, and buy a sheet deep enough to still tuck under. Foam at 4cm rarely causes trouble. Fibre at 10cm often does.
Weight matters too. A deep fibre topper is awkward but liftable. A king-size foam slab is heavy and floppy, which makes changing sheets a two-person job in a small bedroom. If yours slides about once it is on, How to Stop a Mattress Topper from Sliding: The Ultimate UK Anti-Slip Guide is the fix.
So which should you buy?
Answer two questions honestly.
- Is the problem pressure or padding? Specific aches at hip and shoulder on a hard mattress point to memory foam. A bed that feels thin, flat or unwelcoming points to microfibre.
- Do you run hot, and will you want to wash it? Two yeses point firmly at microfibre, whatever the first answer was.
Side sleeper on a hard mattress who sleeps cool: foam. Anyone softening a tired guest bed, a teenager's bed, or a bed in a warm room: fibre. Hot sleeper who still needs pressure relief: shallow foam under a breathable cover, and nothing deeper.
Both of ours, plus the protectors that should go over whichever you pick, are in Mattress Protector & Toppers. If you would rather work through every material before deciding, Which is the Best Mattress Topper in the UK? Expert Buyer's Guide covers latex, wool and feather as well, and Top Rated Memory Foam Mattress Topper Guide goes deeper on foam specifically.