Watch Water Resistance: Understanding ATM and BAR Ratings

Rain, hand washing, showers, swimming… How much water can your watch really withstand?

Water resistance is an important feature to consider when choosing a watch. Yet the ratings displayed on a watch dial or product page, such as 3 ATM, 5 ATM or 10 ATM, are often misunderstood.

Can a watch rated to 50 metres really be worn at that depth? Can you shower while wearing a 5 ATM watch? And what about leather straps?

This guide explains what these ratings actually mean and how to care for your watch to help preserve its performance over time.

1. What Does Water Resistance Mean?

Water resistance refers to a watch's ability to prevent water from entering its case and damaging its movement.

This protection relies on several components: the seals, crystal, case back and crown. Together, they form a barrier designed to protect the movement against moisture and water ingress.

Water resistance is generally expressed in ATM or BAR.

• 1 ATM = 1 BAR, approximately equivalent to the pressure exerted by a 10-metre column of water.

• 3 ATM = 3 BAR

• 5 ATM = 5 BAR

• 10 ATM = 10 BAR

• 20 ATM = 20 BAR

Please note: these figures refer to pressure tests carried out under controlled conditions. They do not directly indicate the depth at which a watch can safely be used.

2. Understanding Different Water Resistance Ratings

Each water resistance rating corresponds to different conditions of use. Here is a practical guide to help you understand what your watch can withstand.

3 ATM / 30 metres: Protection Against Light Contact with Water

A watch rated to 3 ATM is designed to withstand splashes and rain.

Suitable for:

• Occasional hand washing, avoiding direct water jets.

• Rain and light splashes.

Avoid:

• Showers and baths.

• Swimming and water sports.

• Prolonged immersion.

This rating is primarily intended for everyday wear, with the watch kept away from water as much as possible.

5 ATM / 50 metres: Enhanced Everyday Water Resistance

A watch rated to 5 ATM offers greater protection against occasional contact with water.

Suitable for:

• Hand washing.

• Rain and splashes.

• Occasional contact with water.

To be avoided as a precaution:

• Showers and baths, particularly because of heat and changes in pressure.

• Swimming, unless specifically approved by the manufacturer.

• Diving and prolonged immersion.

A 5 ATM rating does not mean that the watch can be used at a depth of 50 metres.

10 ATM / 100 metres: Suitable for Certain Water Activities

A watch rated to 10 ATM offers a higher level of protection and may be suitable for certain aquatic activities.

Generally suitable, subject to the manufacturer's recommendations:

• Swimming.

• Surface water sports.

• Recreational bathing.

Avoid:

• Scuba diving, unless the watch has the appropriate certification.

• Activities involving significant pressure changes or strong impacts on the watch.

20 ATM / 200 metres: Designed for More Demanding Water Activities

Watches rated to 20 ATM are designed to withstand more demanding conditions.

Depending on their construction and certification, they may be suitable for certain diving activities and other water sports.

However, it is essential to follow the manufacturer's instructions. A 20 ATM rating does not automatically mean that a watch is a certified diving watch.

3. Why 50 Metres Does Not Mean You Can Dive to 50 Metres

This is probably the most common misconception about watch water resistance.

When a watch is marked 5 ATM or 50 metres, it means that it has been tested to withstand a static pressure equivalent to a 50-metre column of water, under controlled conditions.

Real-life conditions are different.

Arm movements, temperature changes, water jets and variations in pressure can place additional stress on the seals and other components.

This is why a watch rated to 50 metres is not necessarily suitable for swimming or showering.

4. How to Preserve Your Watch's Water Resistance

Even a watch designed to withstand water requires proper care.

Avoid sudden temperature changes

Moving from cold water to a hot shower can place stress on the seals and increase the risk of water ingress.

Never operate the crown underwater

The crown must always be correctly positioned and, if it is a screw-down crown, fully secured before the watch comes into contact with water.

Avoid using push-buttons underwater

Unless specifically approved by the manufacturer, never operate a chronograph's push-buttons while the watch is submerged.

Rinse your watch after exposure to salt water or chlorinated water

For watches approved for such use, rinsing with fresh water helps remove salt and chlorine residue. Dry the watch carefully afterwards.

Have the water resistance checked regularly

Seals naturally deteriorate over time. Impacts, wear and servicing can also affect the watch's original level of protection. Periodic checks by a qualified watchmaker are therefore recommended, particularly before using your watch in water.

5. Special Care for Leather Straps

A water-resistant case does not mean that every part of the watch is suitable for contact with water.

Leather is a natural material that absorbs moisture. Repeated exposure to water can cause it to warp, discolour, harden or wear prematurely.

Even if your watch has a high water resistance rating, we recommend keeping its leather strap away from water.

For water-related activities, choose a watch fitted with a suitable strap, such as silicone, rubber or stainless steel, in accordance with the manufacturer's recommendations.

6. Water Resistance Is Not Permanent

A watch can lose some of its water resistance over time.

Seals may dry out, deform or deteriorate. A fall or impact can also compromise water resistance, even if no visible damage is apparent.

We recommend having your watch's water resistance checked:

• After a significant impact.

• Following any work on the case or crystal.

• Whenever you have doubts about its condition.

• Regularly if you use your watch in water.

If condensation appears inside the crystal, have your watch examined by a watchmaker as soon as possible.

7. Before Wearing Your Watch in Water: A Few Essential Checks

Before taking part in any water activity, make sure you check three things:

1. The water resistance rating stated in your watch's technical specifications.

2. The manufacturer's recommendations, which may be more restrictive than the general water resistance rating.

3. The overall condition of your watch, particularly its seals, crown and crystal.

If in doubt, it is always safer to remove your watch.

At a Glance: Which Water Resistance Rating Should You Choose?

A watch is first and foremost a precision instrument. Respecting its limits and taking proper care of its water resistance will help preserve its movement, appearance and the pleasure of wearing it for many years to come.

Our advice: if you are unsure whether your watch is suitable for use in water, always refer to the specific instructions provided by its manufacturer. Water resistance ratings are technical guidelines and do not replace the recommendations for each individual model.