Bar / ATM Pressure Rating — What This Mark Means
A water resistance rating expressed in bar or ATM (atmospheres) instead of meters. One bar/ATM approximately equals 10 meters of water depth in testing pressure.
What This Usually Means
Bar and ATM are units of pressure used to rate water resistance. They represent the same concept as meter ratings but in different units. The conversion is straightforward: 1 bar or 1 ATM roughly equals 10 meters of static water pressure. Seeing "10 BAR" on your case back means the same as "100M" water resistance.
Where to Find It
On the case back, typically near other water resistance markings. It appears as a number followed by "BAR" or "ATM," such as "10 BAR," "20 ATM," or "5 bar."
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Common Variations
Common ratings include 3 BAR (30M, splash-proof), 5 BAR (50M, rain), 10 BAR (100M, swimming), 20 BAR (200M, diving), and 30 BAR (300M, professional diving). Some brands display both bar and meter equivalents.
Common Misconceptions
People sometimes confuse bar and ATM as different measurements, but they're nearly identical (1 ATM = 1.01325 bar). Also, the bar rating doesn't represent the actual safe depth for activities; it's a static test pressure with the same practical limitations as meter ratings.
What to Do Next
Convert the bar/ATM rating to meters by multiplying by 10 for a quick reference. Use the same practical guidelines as meter ratings: 5 bar for splashes only, 10 bar for swimming, 20 bar for diving.
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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
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Frequently asked questions
What's the difference between bar and ATM?
They're essentially the same for watch ratings. 1 ATM equals approximately 1.013 bar, making them interchangeable for practical purposes.
How do I convert bar to meters?
Multiply by 10. So 5 bar equals approximately 50M, 10 bar equals 100M, and 20 bar equals 200M.
Why do some watches use bar instead of meters?
It's largely a manufacturer preference. Japanese and European brands often use bar, while others prefer meters or feet.
Is 3 bar enough for everyday wear?
Yes, for dry conditions. 3 bar (30M) can handle accidental splashes and rain but should avoid any intentional water contact.
Does 10 bar really mean 100 meters deep?
In terms of static test pressure, yes. But in practical terms, the same cautions apply as with any water resistance rating. It's suitable for swimming, not diving.
Can bar ratings decrease over time?
The rating itself doesn't change, but the actual resistance can decrease as gaskets age and degrade. Regular testing is advisable.