Firmness Scale (1-10)
The standard 1–10 mattress firmness rating, where 1 is extremely soft (deep sinkage), 10 is extremely firm (almost no give), and 6 is the medium-firm sweet spot for most sleepers.
The 1–10 firmness scale is a subjective consumer-facing simplification of mattress feel. There is no industry-standardized testing protocol — each brand assigns firmness ratings based on internal subjective evaluation, often calibrated to a 230 lb 'average' tester.
Practical firmness ranges: 1–3 (very soft, deep sinkage, suitable only for lightweight side sleepers under 130 lb), 4–5 (soft, ideal for side sleepers 130–180 lb), 6 (medium-firm, the most popular firmness, works for most body types and sleep positions), 7–8 (firm, best for stomach sleepers, back sleepers over 200 lb, and heavy combination sleepers), 9–10 (very firm, almost no contouring, niche use cases like back-pain rehabilitation).
Firmness perception varies by body weight. A mattress rated 6/10 by a 230 lb 'average' tester feels closer to 7/10 to a 130 lb side sleeper (less compression on lighter bodies) and closer to 5/10 to a 290 lb sleeper (more compression on heavier bodies).
Firmness is not the same as 'support'. A soft mattress can be highly supportive (proper spinal alignment) if the support core is firm enough; a firm mattress can lack support if the coil core is undersized for the sleeper's weight. Don't confuse the two.
The 1-10 firmness scale is a consensus convention, not a standard, and it is body-weight dependent. The same mattress reads a 6 for a 140 lb sleeper and a 4 for a 240 lb sleeper because heavier bodies compress further into the comfort layers. Every firmness claim you read implicitly assumes an average-weight sleeper.
That is why our reviews report firmness alongside body type rather than as a single number. If you weigh under 130 lb, shop about one point softer than the rating you think you want; over 230 lb, shop one point firmer. Ignoring this is the most common reason a well-reviewed mattress feels wrong at home.
What This Means for Shoppers
For 60% of adult sleepers, a 6/10 (medium-firm) is the right starting point. Side sleepers under 180 lb should look at 4–5/10 instead. Back and stomach sleepers over 200 lb should look at 7/10. Always compare firmness ratings within the same brand — cross-brand 6/10 ratings are not directly comparable.