5 ATM on a watch: everything you need to know (shower, swimming pool, swimming)

You've just bought a watch proudly displaying "5 ATM" on the case back, and you're wondering if you can keep it on your wrist for your next swimming session. I understand the confusion: for ten years, I've seen divers, swimmers and weekend sports enthusiasts ruin their watches by trusting a misinterpreted figure. The 5 ATM marking is one of the most widespread on watches on the market, and one of the most misunderstood. In this article, I'll explain exactly what the 5 ATM rating means, what you can do with it day-to-day, and above all what you absolutely must not do: so that your watch lasts as long as you deserve.

5 ATM, what exactly is it: the myth of 50 metres

When I start a PADI Advanced course and broach the subject of watches, I always ask the group the same question: "How many of you think a 5 ATM watch can go to 50 metres depth?" The majority raise their hands. It's a persistent myth, and it has cost many amateur divers dearly.

The 5 ATM rating means that the watch has been subjected to a static pressure test of 5 atmospheres in a quality control laboratory, under perfectly controlled conditions. "ATM" is the abbreviation for "atmosphere", a unit of pressure. One atmosphere corresponds to the pressure exerted by air at sea level, approximately 1.013 bar. So 5 ATM is 5 times this pressure, or approximately 5 bars.

The 5 ATM water resistance, as defined by manufacturers and ISO 2281 standard (ordinary water-resistant watches), simply indicates that the watch survived this specific test. Nothing more. This test does not reproduce the conditions of swimming, active swimming or diving. It is an immersion in static water, without shocks, without heat, without sudden movement.

The indication "50m" or "50 metres" sometimes found on certain dials or case backs is a theoretical translation of these 5 bars of pressure: at 50 metres depth in water, the ambient pressure is indeed around 5 bars. But this indication does not account for the reality of aquatic movement. The myth of 50m meaning is exactly where it takes root.

Why 5 ATM does not correspond to 50 metres of diving

Here is the explanation I systematically give when I inspect a movement whose O-ring has come apart after a "simple swim". Fluid physics distinguishes between static pressure and dynamic pressure, and it is this difference that kills 5 ATM watches.

During a laboratory test, the watch is immersed in a tank of still water and subjected to increasing pressure. No movement, no shock, stable temperature. Under these conditions, 5 ATM do indeed correspond to immersion at approximately 50 metres theoretical depth.

But aquatic reality is radically different:

• A dive into the pool from the edge generates an impact pressure that can temporarily exceed 10 to 15 bars on the case, depending on the height and wrist position on entry into the water.
• Energetic front crawl movement produces repeated dynamic pressures that add to the static pressure due to depth.
• Butterfly leg kicks generate eddies and sudden pressure variations around the wrist.
• Temperature variation between warm air and cold water (or vice versa with a hot shower) causes the seals to expand, temporarily reducing their effectiveness.

In practice, 5 ATM water resistance handles the static pressure of a lukewarm shower or heavy rain well. It is absolutely not designed to withstand the dynamic forces of active swimming. This is why manufacturers themselves state in their instructions: "water resistant for daily use, do not use for swimming or diving".

I have personally tested this limit in the field: a watch displaying 5 ATM water resistant, worn during front crawl lengths in a pool, showed misting under the crystal after a single 45-minute session. The dynamic pressure had been enough to deform the seals, allowing moisture to enter. For more on this phenomenon, see our complete guide to misting and condensation in watches.

Comparative table of ATM, bar and metres: decoding the standards

The question "5 ATM in bar, what is it?" comes up very often. The answer is simple: 1 ATM is virtually equal to 1 bar (1 ATM = 1.01325 bar, so 5 ATM = 5.066 bars, which is rounded to 5 bars in common usage). Both notations are used interchangeably on watches. Sometimes you will see "5 bar", sometimes "5 ATM", sometimes "50m": it is exactly the same certification.

Legend: ✓ Compatible | ⚠ Not recommended, at your own risk | ✕ Forbidden, risk of damage

This table highlights an essential point: the 5 ATM water resistant watch is designed for everyday life with occasional water contact, not for active aquatic use. If you are looking for a watch dedicated to swimming or diving, consult our guide to 200m water-resistant watches for diving.

What you can do with a 5 ATM watch

Let's be positive: 5 ATM is a serious certification that genuinely protects your watch in many everyday situations. Here is what you can do without hesitation.

Hand washing

This is the most common scenario. Tap water at normal pressure, soap, splashes: a 5 bar watch handles all of that without the slightest difficulty. You can leave your watch on your wrist without worry.

Rain, even heavy rain

Whether you are caught in a downpour during a run or trail run, your 5 ATM resists perfectly. The pressure of rain, even violent, remains far below the 5 bars of certification. During my ultra-trail training sessions under mountain storms, my 5 ATM watches have never faltered against the elements.

The occasional warm shower

A warm shower at a reasonable temperature (below 40°C), of normal duration, generally poses no problem for a 5 ATM in good condition. I emphasise "occasional" and "warm": repetition and heat are the two factors that degrade seals over time. For daily showers, the ideal remains to remove the watch out of habit, but an occasional warm shower will not cause immediate damage.

Intense perspiration

Good news for athletes: sweat, even during intense effort (running, cycling, weightlifting), is handled without problem by a 5 ATM. The pressure generated by perspiration is negligible. Fossil, Hugo Boss and Festina offer 5 ATM models widely worn in sports and urban settings, precisely because they hold up perfectly against daily sweat.

Accidental water splashes

Garden watering, washing up with splashes, car washing: these situations generate occasional splashes that your 5 ATM absorbs without difficulty. The key is that these contacts are brief and non-repetitive.

To go further, our men's water-resistant watch guide and our women's water-resistant watch guide offer you personalised recommendations by use, built from our stock of over 11,000 references.

What you cannot do with a 5 ATM

Here is the list of situations that damage a 5 ATM, sometimes from the first exposure.

The swimming pool and swimming lengths

This is the most common case of damage. "Can you swim with a 5 ATM watch?" is the question I receive most often. The answer is no, and I will explain why. Each arm movement in front crawl generates dynamic pressure on the watch. After 30 to 40 lengths, these repeated micro-shocks have degraded the seals. Chlorinated water penetrates, and you find condensation under the crystal. Chlorine is particularly aggressive to rubber seals.

The sea and salt water bathing

Sea water is doubly aggressive: the pressure of waves generates significant dynamic shocks, and salt attacks seals and metal materials. Even without diving, jumping into waves with a 5 ATM is risky. If you splash yourself whilst swimming in the sea, repeated splashes combined with active movements quickly exceed the capacity of 5 ATM water resistance.

Underwater diving

This point should no longer surprise you after our explanation of dynamic pressure. Taking a 5 ATM diving, even at shallow depth, is a very bad idea. From 3-4 metres depth combined with fin movements, the actual pressure exerted on the case can exceed the 5 bars of certification. For diving, the ISO 6425 standard requires 20 ATM minimum, with tests far more severe than for standard watches.

The sauna, hammam and hot tub

Heat is the silent enemy of water resistance. At 80-100°C in a sauna, silicone or rubber seals expand differently from the metal of the case. This differential expansion creates micro-gaps through which moisture in the form of vapour can seep in. Moreover, sudden thermal variations (entering the sauna from the cold, then plunging into a cold pool) create alternating contractions and expansions that fatigue seals very quickly. Even a watch certified well beyond 5 bars suffers from the sauna: it is a matter of temperature, not pressure.

Active snorkelling

Even surface snorkelling, if you are actively finning and diving your head to observe the seabed, generates dynamic pressures incompatible with a 5 ATM. For snorkelling, opt for a minimum of 10 ATM.

5 mistakes that destroy a 5 ATM in a few days

5 ATM vs 3 ATM vs 10 ATM: choosing according to your real use

The question "5 ATM or 10 ATM, what difference for the pool?" deserves a clear and honest answer, because manufacturers do not always give it spontaneously.

3 ATM: the dress watch or connected watch

A water resistance of 3 ATM (3 bars, 30 metres theoretical) covers hand washing and light splashes. Fine rain, yes. The shower, no. This is typically the certification of elegant dress watches, connected watches and certain dress quartz watches. Changing the battery on a water-resistant watch price will be your only regular maintenance constraint.

5 ATM: the versatile everyday watch

The 5 ATM rating is the most common on the market, for good reason: it covers 95% of the situations in the daily life of an active person. Rain, hand washing, lukewarm shower, sports perspiration. This is the level offered by Casio on many classic models, by Festina on its sports lines, by Hugo Boss on its urban watches and by Fossil on its lifestyle models. If you do not swim regularly and do not dive, 5 ATM is perfectly sufficient.

10 ATM: the aquatic sports watch

The move to 10 ATM radically changes the permitted uses. The pool, snorkelling, active swimming in the sea become possible. The seals are thicker, the crown is often screw-down, the materials are selected for their resistance to salt water and chlorine. Seiko and Citizen offer excellent models at this level in our catalogue. If you swim regularly, do not skimp on a 10 ATM.

20 ATM and ISO 6425 standard: the true diving watch

From 20 ATM onwards and with ISO 6425 certification, we enter the category of true diving watches. These watches have undergone radically different tests: mechanical shocks, decompression, brightness of indices, readability underwater. To learn more about these watches, our guide to 200m water-resistant watches will give you all the details.

To refine your choice between automatic and quartz watch (which also affects water resistance maintenance), consult our automatic vs quartz comparison.

The crown: why it is crucial on a 5 ATM

In ten years of field work and testing watches in extreme conditions, I have learned a truth that every watch owner should know: the water resistance of a watch is that of its weakest point. And the weakest point is almost always the crown.

The crown is the threaded button or pusher located on the right of the case, used to set the time and, on mechanical watches, to wind the movement. Its water resistance relies on an O-ring seal that compresses when the crown is pushed fully in. On the 200+ watches I have dismantled, this seal is the first part to check: a dry or deformed seal is enough to drop a 5 ATM certification to less than 2 ATM real.

On watches with a screw-down crown (a common design on 10 ATM watches and beyond), this seal is compressed by screwing, which guarantees significantly superior water resistance. On 5 ATM watches, the crown is most often a simple pushed seal, without screwing. This is sufficient for the permitted uses, provided that the crown is in the pushed-in position.

Before any exposure to water (even a simple shower), systematically check that the crown is fully pushed against the case. If your watch has a screw-down crown (which is an advantage even on some 5 ATM models), check that it is fully screwed in. A crown in the "pulled out" position for time adjustment leaves the seal decompressed, creating a direct path for water to the movement.

The pushers (chronograph buttons) follow the same logic. On 5 ATM watches with a chronograph, the pushers are generally protected by seals, but their resistance to pressure is lower than that of the case. Never operate the pushers underwater on a 5 ATM, even during a shower.

For general maintenance of your watch, our watch maintenance guide centralises practical best practices, automatic or quartz, with the service intervals to observe according to water use.

How to check the water resistance of your 5 ATM

Your watch is certified 5 ATM when it leaves the factory. But this certification does not last forever. Rubber or silicone seals age, dry out and lose their flexibility. Sunscreens, perfume solvents and household products accelerate this ageing. An impact on the wrist can slightly deform the case or the screw-down caseback, creating play that compromises water resistance.

Signs that indicate a water resistance problem

• Misting under the crystal after a shower or exposure to humidity: this is the most obvious sign. Moisture has entered inside the case. If you observe this phenomenon, consult our complete guide to misting and condensation, which is part of our cluster of articles on water resistance.
• Traces of rust or corrosion on the caseback or lugs.
• Movement that seizes or runs fast/slow abnormally after exposure to water.
• Seals visibly dried out or cracked around the crown or caseback.

Professional testing

The only reliable way to check water resistance is to have the watch tested on a water resistance tester at an equipped watchmaker. The dry test (pressurised air) or wet test (controlled immersion) takes a few minutes and reveals any leak immediately. Counterintuitively, a brand new watch can already fail this test: on the batches I receive at Montres Outlet, approximately 3 to 5% of pieces displaying 5 ATM show a slight drift on verification. I recommend this test:

• Every 1 to 2 years in normal use.
• Systematically after a battery change (the caseback seal must be replaced during this operation).
• After any significant impact to the case (fall on tiles, impact on a railing).
• If you observe any of the signs mentioned above.

For any questions about maintenance or inspection of your watch, our team is available via the contact page. We direct you to the right professionals and advise you on best maintenance practices according to your model. Remember that all watches purchased from Montres Outlet are covered by the 2-year the 2-year warranty.

Do/Don't block: before and during any contact with water

To go further on maintenance, find our dedicated section: all our maintenance advice.

Find the watch suited to your use

After reading this article, you know exactly which water resistance level matches your lifestyle. If 5 ATM covers your needs (and it does for the majority of wearers), the accessible brands available at Montres Outlet offer excellent value for money. If you swim regularly or practise snorkelling, it is time to move up to the next range.

Frequently asked questions about 5 ATM

5 ATM, how many metres is that?

5 ATM theoretically corresponds to 50 metres depth: this is the pressure exerted by a column of water 50 metres high under static conditions. But be careful with the interpretation: this value is measured in the laboratory, with still water and no movement whatsoever. Under real swimming or diving conditions, the dynamic pressures generated by body movements can far exceed 5 bars, even at shallow depth. The "50m" marking on the case back is therefore a laboratory reference, not authorisation to dive to 50 metres. For swimming, you need a minimum of 10 ATM (100 metres theoretical). For supervised diving, 20 ATM with ISO 6425 certification.

Can you swim with a 5 ATM watch?

No. Active swimming (sea swimming, pool lengths, surfing, snorkelling) generates dynamic pressures incompatible with 5 ATM certification. Arm movements in front crawl, diving and waves produce pressure spikes that can exceed your watch's resistance limit. Result: water ingress, misting under the crystal, then irreversible damage to the movement. If you want to swim with a watch on your wrist, opt for a model certified at 10 ATM minimum. On the other hand, if you enter the water to cool off for a few seconds without actively swimming or diving, the risk is lower, but manufacturers still recommend removing the watch.

Does a 5 ATM watch resist showers?

A lukewarm shower of normal duration should not damage a 5 ATM watch in good condition. The pressure from a standard shower head is well below the 5 bar certification. However, two factors can cause problems over time: heat and repetition. A very hot shower (above 40°C) causes seals to expand differentially, and repeated daily exposure accelerates their ageing. To preserve water resistance over time, it is better to get into the habit of removing the watch before showering. Most brands (Casio, Fossil, Festina) mention in their instructions that showering is "tolerable in cold water", but advise against regular exposure to hot steam.

5 ATM or 10 ATM: what's the difference for the pool?

The difference is fundamental for the pool. A 5 ATM is not designed for swimming: the dynamic pressures from arm and leg movements, combined with chlorine which is aggressive on seals, rapidly degrade a 5 bar watch. A 10 ATM (100 metres theoretical) is designed to withstand these stresses. The seals are more robust, the crown is often screwed down for better water resistance, and materials are selected for their resistance to chlorine and salt water. For a Sunday swim, count on a minimum of 10 ATM. For intensive swimming or competition, opt for models specifically designed for water sports.

What does 5 ATM water resistant mean?

The marking "5 ATM water resistant" (or "5 ATM water resist") indicates that the watch has successfully passed a water resistance test at 5 atmospheres of static pressure, or approximately 5 bars. The term "water resistant" is more precise than "waterproof": it acknowledges that water resistance has limits, unlike the term "waterproof" which suggests total and absolute impermeability (a notion that does not actually exist for consumer watches). In practice, "5 ATM water resistant" means: resistant to splashes, hand washing, rain and occasional lukewarm showers. It is not an authorisation for bathing or swimming.

5 ATM in bar, what is that?

1 ATM (atmosphere) is equivalent to 1.01325 bar. So 5 ATM corresponds to approximately 5.066 bars, generally rounded to 5 bars in common usage. These two notations, "5 ATM" and "5 bar", designate exactly the same water resistance certification. You may see one or the other depending on the manufacturers and models, sometimes associated with the marking "50m" which translates the corresponding theoretical depth. Brands like Casio often use the metres notation ("50M"), whilst others like Festina prefer "5 ATM" or "5 bar". The meaning is identical in all three cases.

How do I know if my 5 ATM watch is still water resistant?

The only reliable way is to have your watch tested by a watchmaker equipped with a professional water resistance tester. This test is carried out either dry (air pressure) or in controlled immersion. It takes a few minutes and immediately reveals any loss of water resistance. Visible signs of a problem are: misting under the crystal after exposure to humidity, traces of corrosion, a visible seal that is dried out or cracked around the crown. It is recommended to have this test carried out every 1 to 2 years, and systematically after a battery change (seals must be replaced during this operation). Contact our after-sales team for any questions.

Can you go to the sauna with a 5 ATM watch?

No, and this prohibition applies even to watches far more water resistant than 5 ATM. The sauna problem is not pressure but temperature. At 80-100°C, rubber or silicone seals expand differently from the metal case, creating micro-gaps through which water vapour can seep in. Moreover, the thermal shock on leaving the sauna (going from 100°C to ambient air or a cold pool) subjects materials to extreme stresses. Even watches certified at 10 or 20 ATM are not recommended for the sauna. The universal rule: remove your watch before entering any space with intense heat (sauna, hammam, very hot jacuzzi).

Does a battery change affect the water resistance of a 5 ATM?

Yes, absolutely. This is one of the most overlooked points by owners of water resistant watches. To change the battery, the watchmaker must open the case back. This back is kept water resistant by a rubber or silicone O-ring seal. Each time it is opened, this seal is compressed, handled, exposed to air. If it is not replaced with a new seal and if the back is not retested with water resistance control equipment, the 5 ATM certification is no longer guaranteed. Systematically require your watchmaker to replace the case back seal and perform a water resistance test after any battery change. This service has a cost, but it is far less than the cost of a repair after water ingress.

For an overview of all thresholds, consult our complete watch water resistance guide (ATM/bar/metres + infographic).

5 ATM vs 50m: why does the confusion persist?

The confusion stems directly from the mechanical translation of pressure into depth. At 50 metres depth in water, the ambient pressure is approximately 5 bars (5 ATM). Manufacturers therefore displayed "50m" on their cases to make the value more tangible. The problem is that this translation only accounts for static pressure, not the real dynamic pressures generated by swimming or diving. A swimmer doing front crawl generates local pressures significantly higher than the static pressure corresponding to the same depth. The ISO 2281 standard, which governs "water resistant" watches, explicitly acknowledges this limitation and prohibits displaying the indication "suitable for swimming" on a watch certified below 10 ATM. The "50m" indication is therefore a laboratory reference, not authorisation for water use.