WATER RESISTANCE MARKINGS ON WATCHES — WHAT DO THEY REALLY MEAN?
Water resistance markings are among the most commonly misunderstood indicators on a watch. Numbers like "50M", "100M", or "10 BAR" appear on case backs and dials, but their meaning often differs from what buyers expect. Understanding these markings can help you make informed decisions about what activities are safe for your timepiece.
What Water Resistance Markings Typically Indicate
Water resistance ratings on watches follow standards set by organizations like ISO (International Organization for Standardization). The most common standard is ISO 22810, which replaced the older ISO 2281. However, it's important to understand that these ratings are tested under controlled laboratory conditions and may not perfectly reflect real-world use.
A "30M" or "3 BAR" rating generally suggests the watch can withstand splashes but is not typically recommended for swimming. A "50M" or "5 BAR" marking often indicates suitability for brief immersion, such as shallow swimming. Watches marked "100M" or "10 BAR" are commonly considered adequate for recreational swimming and snorkeling. Ratings of "200M" or above are frequently associated with diving watches.
Common Formats and Variations
Water resistance can be expressed in several ways:
- Meters (M): e.g., "WR 50M", "WATER RESISTANT 100M"
- Bar (BAR): e.g., "10 BAR", "20BAR"
- ATM: e.g., "5 ATM", "10 ATM" (atmospheres)
- Feet (ft): Less common, primarily seen on American-market watches
The relationship between these units is approximately: 1 ATM ≈ 1 BAR ≈ 10 meters. However, some manufacturers round differently, so minor discrepancies can occur.
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Important Caveats
Water resistance is not a permanent feature. Gaskets and seals can degrade over time, especially with exposure to chemicals, extreme temperatures, or physical impacts. Most watchmakers recommend having water resistance tested annually if the watch is regularly exposed to water.
Additionally, the ratings assume static pressure. Activities like diving, water skiing, or even turning a faucet on a submerged wrist can create dynamic pressure that exceeds the static rating. Always err on the side of caution.
What to Check Next
If you've found a water resistance marking on your watch, you may also want to examine the case-back for the case material marking, the model number stamp, and any manufacturer-specific codes that can help identify your exact model and its original specifications.
Related Markings
A marking indicating the watch's tested water resistance depth, typically shown in meters, feet, bar, or ATM. This ratin
WR 50M / 5 Bar MarkingA water resistance rating of 50 meters (5 bar/ATM), indicating the watch can handle everyday moisture like rain and hand
WR 100M / 10 Bar MarkingA water resistance rating of 100 meters (10 bar/ATM), generally considered suitable for swimming and recreational water
WR 200M / 20 Bar MarkingA water resistance rating of 200 meters (20 bar/ATM), suitable for serious water sports and recreational scuba diving. T
Bar / ATM Pressure RatingA water resistance rating expressed in bar or ATM (atmospheres) instead of meters. One bar/ATM approximately equals 10 m
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Frequently asked questions
Does a 50M water resistance rating mean I can swim to 50 meters deep?
Not exactly. The 50M rating is tested under static laboratory conditions. In practice, a 50M-rated watch is generally considered suitable only for brief, shallow water exposure like hand washing or light rain. Dynamic pressure from swimming strokes can exceed the static rating.
What is the difference between BAR and ATM ratings?
BAR and ATM are nearly identical pressure units. 1 BAR is approximately equal to 1 ATM (atmosphere), and both roughly correspond to 10 meters of water depth. The difference between them is negligible for practical purposes.
Can a watch lose its water resistance over time?
Yes. The gaskets, O-rings, and seals that provide water resistance can degrade due to age, chemical exposure, temperature extremes, and physical wear. Most manufacturers recommend periodic water resistance testing, typically annually for watches regularly exposed to moisture.
Is 100M water resistance enough for swimming?
A 100M (10 BAR) rating is commonly considered adequate for recreational swimming and snorkeling. However, it is generally not recommended for high-impact water sports or scuba diving. Always consult the manufacturer's specific guidelines for your watch model.
What does 'WATER RESIST' without a number mean?
A watch marked only 'WATER RESIST' or 'WATER RESISTANT' without a specific depth or pressure rating typically offers minimal protection, often equivalent to about 30M or 3 BAR. This usually means it can handle incidental splashes but should not be submerged.
Why do some watches show both meters and BAR?
Some manufacturers include both units for clarity, since different markets may be more familiar with one unit over the other. When both are present, they should correspond — for example, 100M and 10 BAR indicate the same rating.
Should I shower with my water-resistant watch?
Most watchmakers advise against showering with a watch, even if it has a reasonable water resistance rating. Hot water and steam can cause thermal expansion of gaskets, potentially allowing moisture to enter. Soap and shampoo chemicals can also accelerate gasket degradation.
How can I get my watch's water resistance tested?
Most watch repair shops and authorized service centers can perform water resistance testing using specialized equipment that pressurizes the case without submerging it. This is a relatively quick and inexpensive procedure that can help confirm your watch's current seal integrity.
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