Best firm mattress toppers, ranked for a mattress that has gone too soft

Sleep On Latex sells its Pure Green topper in Soft, Medium and Firm, and it publishes what each grade means: the Firm is 5.9 lb per cubic foot and 46 lbf at 25% compression, tested to an ASTM foam standard, against 20 lbf for the Soft. The latex is GOLS certified organic, and Sleep On Latex says its firm foam is strong and supportive but not rigid or stiff, which is what you want on a bed that has gone soft: support without a slab.

The brand's own advice is useful too. To firm up a mattress that is too soft, it says to use at least 2 inches and preferably 3; we link the 2-inch, and the 3-inch Firm is worth the step up if your bed feels soft right through. It comes bare unless you buy one of the brand's organic cotton covers, and Sleep On Latex says most customers skip the cover and use a fitted sheet. It costs more than the foam picks here, and latex is heavy to move. Best for back and stomach sleepers who want a properly firm, long-lasting layer and like knowing the numbers.

Latex Mattress Factory makes its firm topper from what it calls 100% natural latex, made by the Dunlop process, and sells it in two grades: Firm at 38 ILD and X-Firm at 44 ILD. Amazon carries only the Firm in a 2-inch layer, which is the one we link. That is a sensible middle choice for a mattress that has gone a little soft, and the brand itself suggests Firm for sleepers who want a firmer, more supportive surface on a bed that is not badly worn.

If your mattress is properly soft, the brand's advice is to start with X-Firm instead, and that grade, like the 3-inch, is only on the brand's own store. The product page states no warranty length, trial or certification, which is less than Sleep On Latex gives you, and there is no cover in the box. The brand says its latex toppers can last up to 10 years with proper care. Best for buyers who want plain natural latex at a published firmness and are happy without the organic paperwork.

The Restore HD is here for a different buyer. ViscoSoft rates its foam at 3.1 lb per cubic foot, which it says is denser than most foam toppers, and describes the feel as medium-firm: it gives at the shoulders and hips and pushes back elsewhere. ViscoSoft pitches it at an older mattress that needs more support or a mattress that is too soft, which is the right job for it. Given the research on medium-firm surfaces, that middle feel may suit a back that dislikes a hard bed.

What it is not is truly firm. If you want a hard surface, the latex picks are firmer, and ViscoSoft says its own 4-inch feels firmer than the 3-inch we link. You do get more in the box than with the latex picks: a removable, machine-washable cover, gel-lined corner straps and a beaded non-slip base, plus a 5-year warranty. Memory foam can sleep warmer than latex despite the gel and airflow channels. Best for sleepers whose mattress has worn soft and who want support back without losing all the cushioning.

BedStory's firm topper costs well under the others and still comes ready to use: a zipped, machine-washable cover and four corner straps. The 3-inch we link is, per BedStory, just under an inch of gel memory foam over about two inches of support foam, and BedStory labels its 2, 3 and 4-inch versions Medium Firm, Firm and Extra Firm. It is refreshingly direct about what the topper is for: it calls it firm, not soft or medium, and says a mattress that sags or is broken down needs replacing instead.

The gap is information. BedStory publishes no density or firmness figure, so you cannot set it against the latex picks on paper, and memory foam softens as it warms. The 365-night trial and 10-year warranty it advertises apply to its own store; an Amazon purchase follows Amazon's return policy. Best for someone who wants to firm up a soft guest bed or a first mattress without spending latex money.