Smart watch water resistance ratings explained

Smart watch water resistance ratings explained: two different scales

Smart watch water resistance ratings explained in one line: ATM measures resistance to water pressure at depth, while IP68 measures dust and water sealing under a lab-controlled submersion test, and the two numbers do not always show up together.

Shopping for a specific model? See our smart watches buying guide — 10 models compared on the specs that decide it.

Two entirely different measurement systems ended up sharing space on the same box, and that overlap is most of the confusion. The ATM scale traces back to ISO 22810, the international standard written specifically for water-resistant watches, and it measures how much pressure a case withstands at a given depth. IP68 comes from a separate lineage altogether: IEC 60529, the general industrial standard for sealing electronics against dust and liquid, applied to everything from outdoor light fixtures to phones long before it ever showed up on a wrist. Smart watch water resistance ratings explained side by side like this make the gap obvious: one measures pressure, the other measures a sealed submersion test, and neither number validates the other.

Smart watch makers borrow from whichever scale suits the listing, and in Buyer Reports's own ten-model smart watch comparison, none mix the two. Some print only an ATM number: the aeac Smart Watch and the Tensky Smart Watch both list 3ATM directly in the title. Others lean on IP68 instead, including the Gydom Smart Watch and the Cillso Smart Watch, neither of which mentions an ATM figure at all. Every listing in that comparison sticks to one system or the other, which is worth remembering: a strong score on the ATM scale says nothing about how the same watch would hold up under an IP68 submersion test, since the two are measuring entirely different things.

How the ATM scale actually works

ATM stands for atmospheres of pressure, and ISO 22810 sets fixed activity tiers for watches: 3 ATM covers splashes and rain, 5 ATM adds showers and shallow swimming, and 10 ATM covers surfing and snorkeling, with diving excluded below 20 ATM.

ATM stands for atmosphere, a unit of pressure equal to what you would feel at sea level, and ISO 22810 assigns a specific set of activities to each tier rather than leaving it to guesswork. 3 ATM, roughly 30 meters, covers everyday splashes, rain, and sweat, but not showering or swimming. 5 ATM, about 50 meters, steps up to include showering, bathing, shallow-water swimming, and snorkeling, though diving still is not covered. 10 ATM, about 100 meters, adds surfing, sailing, and other surface water sports, and 20 ATM, roughly 200 meters, is where the standard starts covering skin diving and serious marine work.

None of those meter figures describe a literal safe diving depth, which trips people up constantly. A 5 ATM watch was never tested to survive 50 meters underwater. The number reflects the pressure the case withstood during a single lab test, and pressure at depth, not an actual dive rating, is what the scale is built around.

In the men's smart watch lineup Buyer Reports compared, only two of ten models print a 5 ATM rating: the Jacoosa Smart Watch and the PODOEIL Military Smarty Watch, the latter built around rugged, outdoor use and marketed as having passed a series of military-grade durability tests. Everything else that lists an ATM figure in that comparison stops at 3 ATM, and a handful of models do not publish an ATM number at all, relying on an IP rating or no stated figure instead. Anyone shopping specifically for hiking, running in rain, or general outdoor wear can see how that spread plays out model by model in our men's smart watch guide, which lines up water rating alongside the rest of the durability specs.

How IP68 and other IP ratings work

IP68 is two separate digits under IEC 60529: the first (6) means the case is fully dust-tight, and the second (8) means it survived continuous submersion beyond 1 meter for a depth and time the manufacturer specifies, not a number IEC fixes universally.

IP ratings work as two digits, and each one answers a different question, which is the half of smart watch water resistance ratings explained that trips up more people than the ATM scale does. The first digit, on a 0-to-6 scale, rates protection against solid particles: a 6 means the case is fully dust-tight, tested under vacuum conditions for hours at a time. The second digit, on a 0-to-9 scale, rates protection against liquid. A 7 means the device survived 30 minutes of submersion with its lowest point roughly a meter below the surface. An 8 means continuous submersion beyond that 1-meter mark, though IEC 60529 leaves the exact depth and duration up to the manufacturer to test and publish. The standard sets a floor, not a fixed ceiling.

That detail matters more than it sounds like it should. IP68 by itself does not say whether a watch was tested to 1.5 meters for 30 minutes or 3 meters for an hour, so two products can both wear an identical IP68 badge while having survived genuinely different amounts of water exposure. Several models in Buyer Reports's smart watch comparisons print IP68 without listing a tested depth at all, including the HUAKUA Smart Watches, the Atheewon Military Smart Watches, and the BRUBOSES Smart Watch in the men's lineup, plus the Gydom Smart Watch, the Poounur Smart Watch, and the Cillso Smart Watch in the broader comparison.

Spec sheets can also disagree with themselves. The TORJALPH Smart Watch lists IP68 waterproof right in its own title, then describes itself as IP67 waterproof a few bullet points further down, two different numbers for the same listing. It is a small inconsistency, but a useful reminder to read the actual bullet copy on a product page rather than trusting whichever rating shows up first.

What a rating does not protect against

No ATM or IP rating covers hot water, steam, saltwater or chlorine buildup, or a case that is already scratched or dropped, and every rating describes a brand-new watch, not one that has aged.

None of these ratings account for what happens over months of daily wear. Heat is the part most people do not expect: hot showers, saunas, and hot tubs put far more thermal stress on a watch's rubber gaskets than a cool swim does, and repeated heat cycling is a common way seals lose their grip over time. That holds regardless of whether the box says 3 ATM or 10 ATM, since none of the standard's tiers are tested against sustained heat exposure in the first place.

Saltwater and chlorinated pool water carry their own risk, mostly through residue rather than pressure. Salt crystals and chlorine buildup around the buttons, crown, or charging contacts can work into small gaps that plain fresh water would not reach, which is why rinsing a watch in fresh water and drying it fully after ocean or pool time is worth doing regardless of brand or rated tier.

Age matters just as much as chemistry. ISO 22810's testing methodology checks a single, newly manufactured sample under one static pressure application, not a claim about how that same watch performs after a year of drops, temperature swings, and gaskets that have simply worn thinner. A 5 ATM rating on a two-year-old watch with a scuffed case back is a different proposition than the same rating on a watch fresh out of the box, even though the number printed on it has not changed.

Which rating you actually need

Match the rating to what you will actually do: 3 ATM covers rain and sweat, 5 ATM is the realistic floor for showering or swimming, and no rating in a typical fitness-tracker-style smart watch lineup is built for diving.

If sweat during a run or getting caught in the rain is the worst case you are planning for, 3 ATM covers it without needing to think any harder about the number. Swimmers, or anyone who wants to shower without taking the watch off first, should treat 5 ATM as the real floor, since it is the point where ISO 22810's own activity list explicitly includes bathing and shallow swimming rather than just splashes. Serious snorkelers or surfers are the ones who actually benefit from chasing 10 ATM, and scuba divers need a dedicated dive watch rated well past anything in a typical fitness-tracker-style smart watch lineup.

Budget and mid-range smart watches cluster around 3 ATM to 5 ATM almost universally, and that is exactly what shows up across Buyer Reports's own comparisons. Our best smart watches guide lines up ten models side by side, several rated 3ATM and one stretching to 5ATM, spanning value tiers from budget to premium so the water rating can be weighed against battery life, display size, and health sensors rather than judged on its own.

Smart watches explained: where water resistance fits on the spec sheet

Water resistance is one spec among several. Battery life, display type, health sensors, and phone compatibility all matter just as much, which is why weighing smart watches explained feature by feature works better than chasing one number alone.

Water resistance is one line on a longer spec sheet, and it is worth treating it that way instead of the single spec that decides a purchase. Battery life, display type, health sensors, and phone compatibility all matter just as much day to day, which is part of why smart watches explained one spec at a time is more useful than chasing a single number in isolation. Buyer Reports's smart watches hub breaks the category down that way, covering the full range of models rather than just the water rating alone.

None of that changes the core lesson here. Smart watch water resistance ratings explained honestly means treating ATM and IP68 as lab results, not lifestyle guarantees. Check the actual number rather than the word printed next to it, rinse the watch after salt or chlorine exposure, skip the sauna, and the rating on the box will hold up about as well as it is built to.