Mattress Calculator By Sleep Position And Weight

1. Pick your main sleep position. Choose the position you wake up in most often. If you change a lot, pick a mix of positions.
2. Enter your body weight. Heavier bodies sink further into a mattress, so weight shifts the firmness you need.
3. Answer the comfort questions. Back pain, sleeping hot, sharing the bed and the age of your mattress refine the advice.
4. Add your partner if you share. Enter the second sleeper position and weight to get a firmness for each side of the bed.

For most people a medium-firm mattress is best. A 2021 review of 39 studies found that medium-firm mattresses gave the best combination of comfort, sleep quality and spinal alignment, including for people with low back pain.

Within that, your position matters. Side sleepers need enough give for the shoulder and hip to sink in, so the spine stays straight. Stomach sleepers need the opposite: a firmer surface so the hips do not sag and arch the lower back. Back sleepers sit in between.

Firmness labels are not standard between brands, so a 6 from one company can feel like a 7 from another. Use the score as a guide, not a guarantee.

It starts from a firmness for your sleep position, adjusts for weight, then keeps people with back pain in the medium-firm band.

The medium-firm target comes from research. The position, weight and thickness steps are common fitting guidance used across the mattress industry, not results from trials, so treat them as a starting point.

Without back pain the same person would get a firm 7.5. The back pain limit keeps the result in the medium-firm range that studies favour, while the extra thickness and zoning cope with the higher load.

Construction matters less than how the mattress supports you. Any type can work if the firmness keeps your spine in line.

Two people rarely need exactly the same firmness. The couples mode scores each side separately, using the same position and weight rules, then compares the two.

When the gap is larger, three kinds of bed are worth comparing. A split-firmness or dual-comfort bed lets each half have its own feel; some are two separate mattresses side by side. A zoned mattress varies support along its length, which helps when the main difference is weight at the hips. The cheapest route is a topper on the side that needs to be softer. Whatever you choose, look for low motion transfer so one person turning over does not wake the other.

Sometimes. A topper is a 1 to 4 inch layer that sits on the mattress and can make it noticeably softer or, with a dense foam or latex, a little firmer. It suits a mattress that is in good shape but feels wrong, or one partner who wants a softer side.

A topper cannot fix sagging underneath; it can only cover slight indentations for a while. A mattress pad, usually 1 to 2 inches, changes the feel even less. If your bed is worn rather than simply too firm, the mattress replacement calculator weighs replacing against a topper, and the sleep accessory cost calculator compares their cost per night.

Body Weight And Shape

A study of side-lying men found spine alignment changed significantly between soft and firm surfaces, and that heavier men with pronounced body contours did best on zoned support.

Back Pain

Medium-firm mattresses have the strongest evidence. Very firm mattresses are not better for backs, despite the old advice.

Pillow

The mattress sets how far your shoulder sinks, which changes the pillow height you need. Recheck it with the pillow height calculator after changing mattress.

Room Temperature

A warm room adds to a warm mattress. Check your bedroom with the sleep temperature calculator.

• Anyone shopping for a new mattress who wants a firmness to aim for.
• People waking with back, shoulder or hip discomfort on their current bed.
• Couples choosing a bed that suits two people.
• People unsure whether to replace an old mattress, who want a firmness to aim for if they do.

Buying The Firmest Mattress For Back Pain

Medium-firm beats firm in the research.

Trusting The Brand Firmness Number

There is no shared scale. Read how it feels to people of your size and position.

Judging In A Few Minutes

Lying on a mattress in a shop for two minutes says little. Prefer a home trial of several weeks.

Keeping A Worn-Out Mattress

Sagging and lumps undo good support. People in a study slept better on new beds than on their roughly 9.5-year-old ones.

The calculator gives a sensible target based on research and fitting guidance, but comfort is personal and brand firmness scales differ.

Medium-firm suits most people and has the best research support, including for low back pain. That is roughly 5.5 to 7 on a 10-point scale.

Side sleepers usually do best on a medium mattress, around 5, with a soft comfort layer so the shoulder and hip can sink in.

A medium-firm mattress. Studies found it gave better comfort and sleep quality than firm mattresses for people with low back pain.

Usually a little firmer and thicker, with zoned support, because heavier bodies sink further into the mattress.

A firmer mattress, around 7, so the hips do not sink and arch the lower back.

Most people do well with 10 to 12 inches. People over about 230 lb often prefer 12 inches or more.

Replace it when it sags or no longer feels supportive. In one study, people with beds around 9.5 years old slept better on new ones.

Memory foam and pocketed-coil hybrids limit motion transfer, so one person moving is less likely to wake the other.

High enough that you can sit on the edge with your feet flat on the floor and knees bent. A typical frame of 12 to 16 inches plus a 10 to 15 inch mattress gives that for most adults; people with limited mobility may want a lower or thinner setup.

• Caggiari et al. What type of mattress should be chosen to avoid back pain and improve sleep quality? (2021) (medium-firm, 39-study review)
• Jacobson et al. Changes in back pain, sleep quality and stress after new bedding systems (2009) (old beds vs new medium-firm beds)
• Leilnahari et al. Spine alignment in men during lateral sleep position (2011) (surface stiffness, zoning and body shape)
• Sleep Foundation. Mattress pad vs mattress topper (toppers 1 to 4 inches; cannot fully restore an old mattress)
• Sleep Foundation. Bed frame sizes (frame 12 to 16 inches; feet on the floor when seated)