How to choose a mattress: the quick answer
Choose your firmness first, then everything else. Work out how you sleep (side, back, stomach or a mix) and how much you weigh, use those two facts to find your spot on the 1–10 firmness scale, and only then pick a mattress type that fixes your specific problems — heat, a restless partner, weak edges. Set a budget based on real sale prices, not inflated list prices, and buy from a brand whose trial lets you return the bed without a fight.
If you want the shortest possible version: most adults between 130 and 230 lb do best on a medium-firm mattress (roughly 5.5–7 out of 10). That is where the clinical evidence lands, it is where most good mattresses sit, and it is the least risky choice if you don’t know what you like. Side sleepers and lighter people should go a little softer; stomach sleepers and heavier people a little firmer. Everything else on this page is about refining that starting point so you get it right first time.
313
Patients in the Kovacs trial
Medium-firm beat firm for chronic low-back pain (The Lancet, 2003)
6–8 yrs
Typical mattress lifespan
Sleep Foundation’s replacement guideline
365
Nights of trial
Saatva, DreamCloud, Nectar, Puffy and Bear, Oct 2026
We don’t run a sleep lab, and we won’t pretend we slept on every bed. What we do is read the evidence other people publish — randomised trials and reviews on mattress firmness, RTINGS’ lab measurements, scores from Sleep Foundation, Tom’s Guide, Mattress Clarity and Sleepopolis, owner reviews, and the brands’ own trial and warranty terms — and turn it into a single, opinionated recommendation. Our how we rate page explains the weighting.
How to choose the right mattress: the 7-step framework
Most buying guides throw twenty factors at you at once. That is why choosing a mattress feels overwhelming. The trick is order. The first three steps decide how the bed should feel — and feel is the thing you can’t fix later without a topper or a return. The last four steps decide which product delivers that feel at a price and with terms you can live with. Answer them in order and each step cuts the field down before the next.
How to choose a mattress: the 7-step decision flow
Answer each question in order — each step narrows the field before the next one. Steps 1–3 decide feel; 4–7 decide the product.
- 1
Sleep position
Side, back, stomach or mix?
→ Sets your starting firmness
- 2
Body weight
Under 130, 130–230, over 230 lb?
→ Shifts firmness ±1–2 points
- 3
Firmness
Your target on the 1–10 scale
→ Most people land on 5–7
- 4
Type
Foam, hybrid, innerspring, latex?
→ Solves heat, motion, edges
- 5
Size
Who sleeps in it, how big is the room?
→ Queen for most couples
- 6
Budget
Real sale price, not list price
→ $650–$1,100 sweet spot
- 7
Trial & warranty
Nights, break-in, return fees
→ Your safety net
✓ Shortlist of 2–3 mattresses → buy the one with the best trial
Each step below ends with a link to the guide that goes deeper on that decision, so you can stop reading here and jump straight to the part you are unsure about. If you’d rather let a tool do the maths, our 30-second mattress finder runs exactly this framework against every model we track; it is also embedded at the end of this guide.
Step 1: Start with your sleeping position
Your sleeping position decides where your body puts pressure on the mattress, and therefore how much give you need. The goal in every position is the same: keep your spine in roughly the same neutral line it has when you stand up straight, while spreading pressure so no single point aches by morning.
- Side sleepers load the shoulder and hip, the two widest and boniest parts of the body. They need a surface soft enough for those points to sink in, or the spine bends upward at the waist and the shoulder goes numb. Sleep Foundation’s guide puts most side sleepers between medium-soft and medium-firm.
- Back sleepers need the lower back supported and the hips kept from sinking. A medium to firm surface with light contouring works best — enough give to fill the curve of the lumbar spine, not so much that the pelvis drops.
- Stomach sleepers need the firmest bed. When the hips sink on a soft mattress, the lower back arches into a hammock shape that many stomach sleepers feel as morning pain. Sleep Foundation’s general advice for stomach sleepers is simply “firm”.
- Combination sleepers who switch through the night should pick for the position they spend most time in. If there is no main position, Sleep Foundation recommends medium-firm, and a bouncier bed that makes turning easy.
Be honest here. Many people describe themselves as back sleepers because they fall asleep that way, then spend most of the night on their side. If you wake up on your side, or with one arm numb, you are a side or combination sleeper. A partner’s observation is usually more reliable than your own memory.
Step 2: Factor in your body weight
Firmness is not an absolute property of a mattress; it is how the mattress feels to you. A lighter person doesn’t sink far enough to reach the softer comfort layers, so the same bed feels firmer to them. A heavier person compresses the comfort layers quickly and reaches the support core, so the bed feels softer — and if the core isn’t strong enough, the hips sink out of line. This is why a bed that every review calls “medium-firm” can feel like a board to one partner and a hammock to the other.
Sleep Foundation splits its recommendations into three weight groups, and it is a useful frame:
- Under 130 lb: softer mattresses usually work better. Recommended range: soft (2–3) to medium (5).
- 130–230 lb: follow the position-based guidance. Recommended range: medium-soft (4) to medium-firm (6), firmer for back and stomach sleepers.
- Over 230 lb: firmer mattresses are generally better. Recommended range: medium-firm (6) up to firm and extra firm (7–10), with thicker comfort layers and a coil core.
Lab data shows the same effect from the other side. RTINGS scores many mattresses separately for light, average and heavy sleepers, and the gaps can be large: on the Saatva Classic in Luxury Firm, side-sleeping scores range from 5.9 for light sleepers to 8.4 for heavy sleepers. RTINGS rates the Puffy Lux Hybrid 7.8 for side sleepers overall but 8.9 for heavier side sleepers. Same bed, very different verdict.
If you weigh over 230 lb, body weight should override almost every other preference. Default to a hybrid or innerspring rather than all-foam, because foam bases can bottom out; look for reinforced edges; and check the brand’s weight rating. The Saatva HD is built for 300–500 lb sleepers and rated to 500 lb per side, one of very few beds engineered specifically for that range.
Step 3: What firmness mattress do I need?
Now combine the first two answers. The chart below plots Sleep Foundation’s recommended firmness ranges for each position and weight group on the standard 1–10 scale. Find your row, note the range, and that is your target. Most people land somewhere between 5 and 7.
The mattress firmness scale, and where you belong on it
Ranges from Sleep Foundation’s firmness guide. The medium-firm zone (5.5–7) is where the clinical evidence clusters.
Side sleepers
Back sleepers
Stomach sleepers
Combination sleepers
Shaded mint column = medium-firm zone. Bar colour: pink under 130 lb, blue 130–230 lb, dark blue over 230 lb.
Why medium-firm is the default. The best-known evidence comes from a randomised, double-blind trial published in The Lancet in 2003. Kovacs and colleagues gave 313 adults with chronic non-specific low-back pain either a firm mattress (2.3 on the European H-scale) or a medium-firm one (5.6). After 90 days, the medium-firm group was more likely to report improvement in pain while lying in bed and in disability. Later reviews reached the same conclusion: Radwan and colleagues’ 2015 systematic review in Sleep Health and Caggiari and colleagues’ 2021 review in the Journal of Orthopaedics and Traumatology both found medium-firm to be the best general recommendation. A smaller study by Jacobson and colleagues reported less back pain and better sleep after people moved to new medium-firm bedding, though it was industry-funded.
Why “firm is better for your back” is a myth. The old advice to sleep on a hard board came from an era of soft, sagging innersprings. The research above compared firm with medium-firm directly, and firm lost. What your back needs is support — a core that keeps the spine level — plus enough cushioning to let the shoulders and hips settle. Those are separate properties, and a good medium-firm mattress has both. If back pain is your main reason for buying, our best mattress for back pain guide applies this research to specific models.
Treat brand firmness labels with suspicion. There is no industry standard for the 1–10 scale, and testers regularly disagree with brands and with each other. The DreamCloud Classic Hybrid is labelled “Firm” by the brand, rated 6–7.5 by testers, and measured Medium-Plush at RTINGS. The Puffy Cloud has been rated anywhere from 5 (Sleep Foundation) to 7 (Mattress Clarity and Tom’s Guide). RTINGS is the only outlet we cite that measures firmness with an instrument — in pascals per millimetre — so when sources conflict, we lean on its number.
Practical rule: if your target range straddles two firmness options, pick the softer one if you sleep mostly on your side and the firmer one otherwise. There is an asymmetry worth knowing, too: a soft topper reliably softens a mattress that turns out too firm, but no topper truly fixes a bed that is too soft or sags. So if you are torn and weigh over 230 lb, lean firmer; if you are torn and under 130 lb, lean softer and keep a mattress topper in mind as a backup.
Step 4: Pick a mattress type (types explained)
Here is the counter-intuitive part: mattress type does not decide firmness. You can buy soft or firm versions of every type. What type decides is everything else — how hot the bed sleeps, how much a partner’s movement travels, how firm the edges are, how bouncy it feels and, to some degree, how long it lasts. So choose the type that solves your particular problem.
Mattress types explained: inside, feel and trade-offs
Simplified cross-sections. Price = Sleep Foundation’s average queen MSRP range by type; sale prices run lower (see Step 6).
Memory foam
- Feel:
- Slow sink, body hug
- Wins:
- Motion isolation, price
- Loses:
- Heat, edges
- Avg MSRP:
- $900–$1,300
- Our pick:
- Nectar Premier Memory Foam
Hybrid
- Feel:
- Contour + bounce
- Wins:
- Cooling, edges, heavier bodies
- Loses:
- Weight, price
- Avg MSRP:
- $1,500–$2,000
- Our pick:
- DreamCloud Classic Hybrid
Innerspring
- Feel:
- Bouncy, on-top
- Wins:
- Cooling, edges, hotel feel
- Loses:
- Motion transfer
- Avg MSRP:
- $600–$1,100
- Our pick:
- Saatva Classic
Latex
- Feel:
- Buoyant, springy
- Wins:
- Durability, cooling
- Loses:
- Motion, price
- Avg MSRP:
- $1,600–$2,000
- Our pick:
- Saatva Latex Hybrid
Memory foam. An all-foam bed whose top layer softens with heat and pressure and moulds slowly to your shape. It is the best type for motion isolation — RTINGS measured 8.8 on the Nectar Premier and 8.4 on the Nectar Classic — and usually the cheapest for a given comfort level. Its weaknesses are heat, slow response when you roll over, and soft edges. Best for couples with a light sleeper, lighter side sleepers and tight budgets.
What is a coil mattress? Any mattress whose support comes from steel springs rather than foam. That covers traditional innersprings, where the coils are the main event under a thin quilted top, and hybrids, where the coils sit beneath several inches of foam or latex. Modern coil beds almost all use pocketed coils — each spring in its own fabric sleeve — which move independently and transfer far less motion than the wired-together springs of older beds. Coil beds sleep cooler, feel bouncier and have firmer edges than foam.
Hybrid. The default choice for most people today. Foam or latex comfort layers on a pocketed-coil core give you most of foam’s pressure relief with coil cooling and edge support. Hybrids vary enormously: the DreamCloud Classic Hybrid has a bouncy Euro top and scored 9.0 for edge support at RTINGS, while the Puffy Lux Hybrid is plush and pressure-relieving. Best for hot sleepers, heavier bodies, combination sleepers and edge sitters.
Innerspring. The traditional coil bed, now often built coil-on-coil with a pillow top. The Saatva Classic is the best-known example and earned a perfect 10 for temperature control from Sleep Foundation — but Mattress Clarity scored its motion isolation just 2.6 out of 5. Best for back sleepers, hot sleepers and anyone who wants a hotel-bed feel; worst for restless partners.
Latex. Foam made from rubber that pushes back immediately rather than sinking slowly. It is the coolest and most durable type: the Saatva Latex Hybrid scored 8.3 for longevity and 8.6 for cooling at RTINGS, the highest of any Saatva. The trade-offs are price, weight and a lively feel that transfers motion. Best for hot sleepers, eco-minded buyers and anyone who wants a bed to last a decade.
Step 5: Choose the right size
Size is the step people skip, and it is the one mistake a trial period can’t fix cheaply — returning a bed because it doesn’t fit the room is a long, annoying process. Two questions settle it: how many people (and pets) sleep in it, and how much floor space do you really have?
- Twin (38 × 75 in) and twin XL (38 × 80 in): kids, bunk beds, dorms and tall solo sleepers.
- Full (54 × 75 in): fine for one adult; tight for two, with only 27 inches of width each.
- Queen (60 × 80 in): the right answer for most couples and most bedrooms, and the size every price on this site is quoted in.
- King (76 × 80 in): the best upgrade if you share with a restless partner, a child or a dog. A split king is two twin XLs, ideal for adjustable bases or couples who need different firmnesses.
- California king (72 × 84 in): narrower but four inches longer than a king — for tall sleepers, not for more space.
Measure the room before you fall for a king. If a bigger bed leaves you squeezing past the dresser, a queen with better motion isolation will often feel more spacious in practice than a king that crowds the room — a restless partner is usually the real reason couples want more width, and motion isolation fixes that too.
Step 6: How much should you spend on a mattress?
Sleep Foundation puts most mattresses between $600 and $2,000 for a queen at list price, with average ranges of roughly $600–$1,100 for innersprings, $900–$1,300 for foam, $1,500–$2,000 for hybrids and $1,600–$2,000 for latex. It also points out that almost nobody pays list price — and in the online mattress market, that is an understatement.
List prices are anchors, not prices. The DreamCloud Classic Hybrid lists at about $1,892 for a queen and typically sells for around $699. The Nectar Classic lists at $1,664 and typically sells for $699. Puffy anchors its prices to an inflated “Total Value” with an always-on code, and Bear routinely runs 30–40% off. Saatva’s discounts are smaller — around 15% most of the year. So compare typical sale prices, never the crossed-out number.
Firmness × price map
Find your feel first, then your budget. Dot size = Research Score.
Our opinionated budget tiers, based on the beds we track:
- Under $400: fine for guest rooms, kids and first apartments. The Amazon budget picks such as the Siena (about $329) and Zinus Green Tea (about $295) are the ones testers rate, but expect weaker edges and durability, especially over 230 lb.
- $650–$1,100: the sweet spot. This is where value peaks. The Nectar Classic ($699), Bear Original ($699), DreamCloud Classic Hybrid ($699) and Nectar Premier ($999) all score well with expert reviewers.
- $1,100–$2,000: you are paying for specific upgrades — better cooling, three firmness options, zoned coils, thicker comfort layers. Worth it if Step 1–4 told you that you need them. The Puffy Lux and Bear Elite Hybrid live here.
- $2,000 and up: latex, specialist and luxury beds such as the Saatva Latex Hybrid and Saatva HD. Higher price buys durability and white-glove delivery, not automatically better sleep.
The honest answer to “how much should I spend on a mattress?” is: enough to get the firmness and type you need from a brand with a fair trial, and not a dollar more. Divide by the years you’ll sleep on it — a $700 bed that lasts seven years costs about 27 cents a night.
Step 7: Read the trial period and warranty fine print
The sleep trial is your safety net, and the fine print decides how good that net is. The headline number has converged: as of October 2026, every partner brand we cover offers 365 nights on mattresses bought direct. The differences are in the details, and they can cost you real money.
Sleep trials compared: nights, break-in and fees
Light segment = minimum nights before a return is accepted. *No processing fee, but delivery/White Glove/recycling fees aren’t refunded. Policies per each brand’s terms, October 2026.
Bar length = nights from delivery (full width = 365)
Saatva warranty: Lifetime
DreamCloud warranty: Forever (dips over 1.5″)
Nectar warranty: Forever (dips over 1.5″)
Puffy warranty: Lifetime limited
Bear warranty: Limited lifetime
Budget beds: Siena (direct) 10 yr · Zinus (direct) 10 yr · Linenspa 10 yr
- Break-in minimums. Most brands won’t accept a return until you have slept on the bed for a while. DreamCloud, Nectar, Puffy and Bear all require 30 nights. DreamCloud also treats a mattress left unopened for more than 90 days after delivery as misused, which voids both the return and the warranty. Mattress Clarity calls 30 days the rule of thumb across the industry, because that is roughly how long your body takes to adjust to a new surface.
- Return fees. Saatva deducts a $99 processing fee from your refund. DreamCloud and Nectar charge no processing fee, but delivery upgrades, White Glove setup and recycling fees aren’t refunded, and DreamCloud doesn’t refund promotional freebies. Puffy and Bear returns are free.
- Return limits. Puffy allows a maximum of two returns per household; Bear allows one return per household, on your first order only. If you suspect you might need to exchange, factor that in.
- Where you buy. Trials generally apply only to direct purchases. Puffy’s policy explicitly covers only beds bought from puffy.com, and brand trials such as Zinus’s 100 nights usually don’t apply on Amazon, where Amazon’s own return window governs instead.
- Condition. Stains and rips can void a return. Use a waterproof mattress protector from night one — it protects both your trial and your warranty.
Warranties are less generous than they sound. “Forever” and “lifetime” warranties cover manufacturing defects and sagging beyond a set depth, not comfort changes. DreamCloud’s and Nectar’s Forever warranties only cover indentations deeper than 1.5 inches, and owners on Trustpilot complain that claims are slow and photo-heavy. Treat the warranty as protection against a defective bed, and use independent durability data — like RTINGS’ longevity scores — to judge how long the comfort will actually last.
Mattress certifications explained: CertiPUR-US, OEKO-TEX, GOLS, GOTS
Certification logos are one of the few parts of a mattress listing you can actually verify, and they answer two different questions: “Is this material free of the worst chemicals?” and “Is it genuinely organic?” Here is what the four you will see most often actually certify.
Polyurethane foam
CertiPUR-US
Made without formaldehyde, ozone depleters, mercury, lead or other heavy metals, and CPSC-regulated phthalates; VOC emissions under 0.5 ppm.
Fabrics, threads, covers
OEKO-TEX STANDARD 100
Every component tested against a list of over 1,000 harmful substances; bedding is checked under the stricter skin-contact class.
Latex
GOLS
Organic latex standard: at least 95% of the latex must come from certified-organic rubber plantations.
Cotton, wool, textiles
GOTS
‘Organic’ grade needs at least 95% certified organic fibres; ‘made with organic’ at least 70%.
CertiPUR-US is the baseline for any bed with polyurethane or memory foam, and nearly every reputable foam or hybrid carries it. It certifies the foam only — not the cover, glue or fire barrier. OEKO-TEX STANDARD 100 covers textiles: covers, ticking, threads. Neither of these says anything about organic content; they are about harmful substances.
GOLS and GOTS are the organic standards. GOLS applies to latex and GOTS to textiles such as cotton and wool, which is why genuinely organic latex beds usually carry both. The Saatva Latex Hybrid uses GOLS-certified organic latex, and RTINGS named it the best organic mattress of 2026. If a listing says “natural” or “eco” without one of these logos, treat it as marketing.
One more thing worth checking on cheap all-foam beds: the fire barrier. Some budget mattresses historically used fiberglass, and Zinus faced a fiberglass lawsuit in 2022 before reportedly moving to rayon barriers. Bear markets its Bear Natural as fiberglass-free and GREENGUARD Gold certified. If it matters to you, ask the brand directly.
How long do mattresses last?
Sleep Foundation’s guideline is to replace a mattress every 6 to 8 years under normal conditions, and it singles out latex as the most durable type, lasting upwards of 8 years. But the real answer depends on materials far more than on the label. The comfort foams are usually the first part to fail, which is why a hybrid doesn’t automatically outlast an all-foam bed.
RTINGS’ longevity scores make the point: the latex-topped Saatva Latex Hybrid scores 8.3, while the coil-based Bear Elite Hybrid scores just 4.3 because of its foam density, and the DreamCloud Classic Hybrid 5.5. Sleep Foundation suggests memory foam density of 5 pounds per cubic foot or more as a durability signal, and thicker (lower-gauge) coils for innersprings.
Replace your mattress when it, not the calendar, tells you: visible sagging or body impressions, waking up stiff or sore, sleeping better in hotels or at friends’ houses, new squeaks, or worsening allergy symptoms. If the bed is only a few years old and simply feels too firm, a mattress topper is the cheaper fix; if it sags, no topper will save it.
How to buy a mattress: 6 mistakes to avoid
The framework above prevents most bad purchases. These are the mistakes we see most often in owner complaints and return policies.
- Buying “firm” for back pain. The trials favour medium-firm. A too-firm bed is one of the most common reasons owners say a mattress hurts.
- Trusting on-site star ratings. Nectar shows 4.8 stars across 55,000+ reviews on its own site; on Trustpilot the brand sits at 1.4. Puffy’s 4.9 is pooled across every model it sells. Read independent sources.
- Judging in five minutes. A store test or a first night tells you little; your body needs two to four weeks to adjust. That is why break-in minimums exist.
- Ignoring your partner. If you share a bed, the lighter sleeper and the heavier sleeper may need different firmnesses. A split king or a bed with several firmness options solves it.
- Forgetting the foundation. Some beds need a solid base — the all-latex Zenhaven, for example, needs a solid foundation rather than slats. Check before you buy, or you can void the warranty.
- Paying list price. With anchored list prices across the industry, the discount is the price. See our best time to buy guide before checkout.
Mattresses that fit the most people
If you work through all seven steps and still want a starting shortlist, these are the beds that suit the widest range of sleepers in the data we track. For the full ranking, see our best mattress of 2026 guide.
Best value hybrid
DreamCloud Classic Hybrid
About $699 for a queen hybrid with edge support of 9.0 and cooling of 7.9 at RTINGS. The default for back and combination sleepers.
Best memory foam
Nectar Premier Memory Foam
Tom’s Guide’s best memory foam of 2025; motion isolation 8.8. For side sleepers and couples under 230 lb.
Best medium-firm
Bear Elite Hybrid
RTINGS’ best medium-firm mattress for most people, in three firmnesses, with edges of 9.7.
Best innerspring
Saatva Classic
Three firmnesses, two heights, white-glove delivery. The hotel-bed choice for back sleepers.
Most durable
Saatva Latex Hybrid
Longevity 8.3 and cooling 8.6 at RTINGS, with GOLS organic latex.
Best under $400
Siena Memory Foam
Medium-firm foam at about $329, with a 180-night trial when bought direct.
If you…
Side sleeper under 230 lb
If you…
Back or combination sleeper
If you…
Stomach sleeper on a budget
If you…
Over 300 lb
If you…
Side sleeper who sleeps hot
If you…
Soft-bed lover
Try the framework: our 30-second mattress finder
The finder below runs Steps 1–6 for you. Choose your position, weight, heat, pain, partner and budget, and it calculates your target firmness and ranks every model we track against it.
Your target firmness
5.0/10 (±1 is fine; firmness feels firmer the lighter you are)
- 1DreamCloud Premier HybridPrice ↗
Hybrid · 5.5/10 · $1,099 queen
- 2Nectar Premier Memory FoamPrice ↗
Memory foam · 6/10 · $999 queen
- 3DreamCloud Classic HybridPrice ↗
Hybrid · 6.5/10 · $699 queen
A starting point, not a diagnosis. Use the trial period — every pick here has 100+ nights.
How to choose a mattress: FAQ
How do I choose the right mattress?
Work in order: identify your main sleeping position, factor in your body weight, use both to find your target firmness on the 1–10 scale, choose a type that solves your problems (heat, motion, edges), pick a size, set a budget based on sale prices, and buy from a brand with a long trial and a fair return policy.
What firmness mattress do I need?
Most adults between 130 and 230 lb do best on medium to medium-firm (about 5–7 out of 10). Side sleepers and people under 130 lb should go softer (3–5); stomach sleepers and people over 230 lb should go firmer (7 or more), per Sleep Foundation’s firmness guide.
Is a firm or soft mattress better for your back?
Neither extreme. A randomised trial of 313 people with chronic low-back pain published in The Lancet found medium-firm mattresses beat firm ones for pain and disability, and later systematic reviews also favour medium-firm.
How much should I spend on a mattress?
For most people, $650–$1,100 for a queen at real sale prices buys a well-reviewed foam or hybrid mattress. Under $400 suits guest rooms; over $1,100 buys specific upgrades like cooling, latex or multiple firmness options. Never judge by the list price.
What is the best type of mattress?
For most people a hybrid is the safest choice: it sleeps cooler, has firmer edges and supports heavier bodies better. Memory foam is better for couples with a light sleeper and tight budgets; latex is best for durability and cooling; innerspring suits back sleepers who like a hotel feel.
How long do mattress trial periods last?
Saatva, DreamCloud, Nectar, Puffy and Bear all offered 365-night trials on direct purchases in October 2026. Most require you to keep the bed at least 30 nights before returning it, and Saatva deducts a $99 return fee.
How long do mattresses last?
Sleep Foundation recommends replacing a mattress every 6 to 8 years, with latex lasting longest. Replace it sooner if it sags, you wake up sore, or you sleep better elsewhere.
What does CertiPUR-US mean?
CertiPUR-US certifies that polyurethane foam is made without formaldehyde, ozone depleters, heavy metals and CPSC-regulated phthalates, with low VOC emissions under 0.5 parts per million. It covers the foam only, not organic content.