Replace a mattress that sags more than about 1 inch, or one past its typical lifespan that leaves you stiff or sleeping better elsewhere. Most last 6 to 8 years. A younger bed with mild sag often needs rotating and a firmer base, and a 2 to 4 inch topper can change its feel.
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How To Use The Mattress Replacement Calculator
- Pick the mattress type and age. Type sets the typical lifespan; if you are not sure, the general 6 to 8 year range is used.
- Measure the deepest sag. Strip the bed, lay a straight edge such as a broom handle across the dip, and measure from its underside to the lowest point. Leave it blank if you cannot measure it.
- Answer the three symptom questions. Waking stiff, sleeping better in other beds and noisy springs are the signs to count.
- Add the warranty length. A deep sag inside the warranty period may be a claim rather than a purchase.
| Result | What it means |
|---|---|
| Recommendation | Replace now, claim on the warranty, rotate and check the base, add a topper, or keep |
| Typical lifespan | The published range for your mattress type |
| Sag reading | Your depth in both units and whether it counts as minor, mild or deep |
| Topper thickness | A thickness range when a topper is a sensible step |
| Warranty | Roughly how many years of cover are left |
| Confidence | How firmly the inputs point to the answer |
What Is A Mattress Replacement Calculator?
It is a decision aid for one question: is it time to replace your mattress, or is there a cheaper step to try first? Age alone does not answer that. A mattress can outlast its typical range if it still supports you, and a young one can fail early.
The calculator weighs three kinds of evidence. Age, compared with the published lifespan for its type. Sag, the most direct sign that support has gone. And how you sleep on it, because waking stiff or sleeping better elsewhere are among the clearest signs that a bed no longer suits you.
It replaces the older mattress age impact estimator at this address, which gave a modelled score rather than a decision.
How Does The Mattress Replacement Calculator Work?
It checks the strongest evidence first and stops at the first rule that fits.
Deep sag, then age past the range plus any sign, then mild sag, then a single sign, then age alone| Situation | Recommendation |
|---|---|
| Sag over 1 inch (2.5 cm) | Replace now, or claim on the warranty first if it is still in force |
| Past the typical lifespan plus 1 or more signs | Replace now |
| Inside the lifespan range plus 2 or more signs | Replace now |
| Mild sag (0.5 to 1 inch), younger than the range | Rotate and check the base |
| Mild sag, inside or past the range | Topper of 3 to 4 inches while you plan a replacement |
| One sign, little or no sag | Topper of 2 to 3 inches (noise alone: check the base) |
| Past the range, no sag, no signs | Keep for now, plan to replace |
| Anything else | Keep and rotate |
The 1 inch line comes from warranty practice: many warranties treat sagging deeper than that as a defect. The 0.5 inch line and the topper ranges are our own conventions, chosen inside the published 1 to 5 inch range for toppers.
Worked Example: An 8-Year-Old Foam Mattress
| Input or step | Value |
|---|---|
| Type and typical lifespan | Foam, 6 to 7 years |
| Age | 8 years, past the range |
| Deepest sag | 1.5 in (3.8 cm): deep |
| Signs | Wakes stiff: 1 of 3 |
| Warranty | 10 years, so about 2 years left |
| Result | Replace: claim on the warranty first, high confidence |
The sag rule fires first. Because the mattress is still inside its warranty, the first step is a claim, with photos and a measurement. With the same mattress at 11 years, the warranty would have expired and the result would be replace now.
How Long Does A Mattress Last By Type?
| Type | Typical lifespan | Main weakness |
|---|---|---|
| Innerspring | 5.5 to 6.5 years | Sagging as coils lose tension |
| Foam | 6 to 7 years | Softening and body impressions |
| Hybrid | 6.5 to 7.5 years | Sagging and softening of the comfort layers |
| Latex | 7.5 to 8.5 years | The most durable of the four |
| Any type | 6 to 8 years under normal conditions | Used when you pick not sure |
These are typical figures, not expiry dates. Cheaper, lower-density builds wear sooner, and higher-density foam or natural latex tends to last longer.
Factors That Change When To Replace A Mattress
Body Weight And Sharing
Heavier sleepers and couples compress a mattress more, so it sags sooner. Children and pets add wear and stains.
The Base Underneath
A foundation with fewer than six legs, or slats spaced too widely, can let the middle dip. Check the maker guidance on slat gaps, because it can affect the warranty.
Rotation And Care
Turning the mattress head to foot every 3 to 6 months spreads the wear, unless the maker says not to; zoned mattresses are the usual exception. A protector guards against spills that can void a warranty.
Whether It Still Fits You
Your needs can change even when the mattress has not. If you replace it, the mattress calculator suggests a firmness and type for your position and weight.
Replace vs Rotate vs Topper Compared
| Option | Fixes | Does not fix |
|---|---|---|
| Rotate and check the base | Uneven wear, sag from weak support underneath | Worn-out foam or coils |
| Topper | Firmness that does not suit you, slight indentations | Sag deeper than about 1 inch |
| Warranty claim | Early sag or defects inside the warranty period | Normal wear and shallow impressions |
| Replace | Everything above | Nothing, but it costs the most |
A topper usually lasts 3 to 5 years and cannot fully restore an old mattress. To compare what a topper and a new mattress cost per night of use, enter both in the sleep accessory ROI calculator; this page does not repeat that maths.
Who Should Use A Mattress Replacement Calculator?
- Anyone waking stiff or sore who wants to know whether the bed is the likely cause.
- Owners of a mattress past 6 years deciding whether to replace now or wait.
- People with a visible dip who want to know whether it may count as a warranty defect.
- Anyone weighing a topper against a new mattress.
A flat, worn mattress also changes how far your shoulder sinks, so recheck your pillow with the pillow height calculator after any change.
Common Mistakes When Deciding To Replace A Mattress
Judging By The Calendar Alone
A well-kept latex mattress can outlast the range; a cheap foam one can fail in a few years.
Waiting For It To Collapse
Sleep usually gets worse well before a mattress looks ruined. A sag over 1 inch is reason enough.
Buying A Topper For A Deep Sag
A topper follows the dip underneath it. It changes the feel, not the support.
Flipping A One-Sided Mattress
Most modern mattresses are built to be rotated, not flipped.
Deciding After One Bad Night
Note how you wake for a week or two before you decide.
Accuracy And Limitations
The lifespans and the 1 inch sag line are published guidance; the decision order, the 0.5 inch line, the topper ranges and the confidence levels are our own conventions.
What It Calculates Accurately
- Where your mattress sits against the typical lifespan for its type
- Whether a sag passes the common 1 inch warranty line
- How many years of warranty remain
What It Does Not Account For
- The exact terms of your own warranty
- Build quality and foam density
- Medical causes of pain or poor sleep
How We Decide Your Recommendation
Mattress Replacement FAQs
How do I know when to replace my mattress?
Replace it when it sags noticeably, when you wake stiff or sleep better in other beds, or when springs have become noisy, especially past about 6 to 8 years.
How much sag is too much in a mattress?
Many warranties treat sagging deeper than about 1 inch as a defect, and at that depth a topper is unlikely to help. Shallower impressions are normal wear.
Can you fix a sagging mattress?
Not really. Rotating it, checking the base and adding a topper can ease mild sag for a while, but only a repair under warranty or a new mattress fixes it.
Will a mattress topper fix a sagging mattress?
No. A thick, dense topper can even out slight dips for a time, but it sits on top of the sag rather than lifting it.
How often should I rotate my mattress?
Every 3 to 6 months is a common rule, unless the maker says otherwise. Zoned mattresses are often not meant to be rotated.
Does a mattress warranty cover sagging?
Sometimes. Early sag past the depth in the warranty terms may be covered; normal wear and shallow impressions usually are not. Read your own terms.
Which mattress type lasts longest?
Latex, at about 7.5 to 8.5 years on average. Innerspring has the shortest typical life, at about 5.5 to 6.5 years.
Can an old mattress cause back pain?
It can contribute. Sagging reduces support and makes it harder to keep the spine aligned. See a doctor if back pain persists or is severe.
Can I use this calculator for an air bed?
Only roughly. There is no published lifespan for air beds in our sources, so choose not sure and rely mainly on the sag and symptom answers.
Sources
- Sleep Foundation. When should you replace your mattress? (6 to 8 years; replacement signs)
- Sleep Foundation. How long should a mattress last? (lifespan by mattress type)
- Sleep Foundation. How to fix a sagging mattress (toppers, rotation, foundations)
- Sleep Foundation. How we determine durability ratings (warranties commonly cover sag over 1 inch)
- Sleep Foundation. Mattress pad vs mattress topper (toppers 1 to 4 inches; last 3 to 5 years)
Related Calculators
For bedtimes and wake-up times in both directions, use the main sleep calculator. Explore every sleep timing, sleep need and bedroom tool in one place.
All sleep toolsThis calculator gives general guidance on mattress wear and replacement. It is not medical advice. See a doctor or physiotherapist about back, neck or hip pain that persists. Spotted an error? Let us know.