How to interpret water resistance (ATM) – avoid costly mistakes
When you buy a new watch, it often says “Water resistance: 5 ATM” or similar in the specifications – but what does that really mean? Is it waterproof enough to swim with? Can you shower with it? Here we explain what water resistance (ATM) actually means – so you don’t accidentally ruin your watch.
| Marking | Water safety | Use |
|---|---|---|
| 3 ATM | Withstands rain | Hand wash, light rain |
| 5 ATM | Shower resistant | Short shower, wash hands |
| 10 ATM | Water resistant | Swimming, beach activities, water play |
| 20 ATM | Waterproof | Snorkeling, water sports, not diving |
| 30 ATM+ | Diving bell | Professional diving with pressure changes |
Are you going swimming or diving – what should you look for?
If you plan to use your watch in water, it is important to look beyond the ATM number. The construction plays a big role. A screw-down crown provides extra sealing and reduces the risk of water ingress. The material of the strap is also crucial. Leather should be avoided in water as it absorbs moisture and can be damaged over time. Rubber, resin and metal perform significantly better in wet environments.
The movement can also play a role. Solar-powered watches are particularly practical for outdoor activities because they don't require battery replacement as often and are often combined with higher water resistance.
What is 1 ATM?
1 ATM corresponds to normal atmospheric pressure at sea level. A watch marked 1 ATM means in practice that it can only withstand very light moisture. It is not intended for contact with water and should not be used in rain, showering or hand washing. Many people think that 1 ATM means 10 meters depth in practice, but this is a theoretical laboratory measurement without movement or temperature changes.
What is 3 ATM?
3 ATM is a common marking on everyday watches. This means that the watch is protected against splashes, light rain and hand washing. However, it is not intended for showering, bathing or swimming. Hot water and steam can also negatively affect the seals.
If you see “3 ATM” in the specification, consider the watch to be splash-proof, not waterproof.
What does 5 ATM mean?
5 ATM means that the watch can withstand short-term contact with water, such as showering or light exposure. However, it is not recommended for swimming for extended periods or for water sports. Movement in water creates higher pressure than static tests, which is why the margins should be taken seriously.
What is 10 ATM?
10 ATM represents a significantly higher level of water resistance. A watch with a 10 ATM rating is suitable for swimming, snorkeling near the surface, and general beach activities. It is designed to handle pressure changes that occur when moving in water.
For many, 10 ATM is a good balance between everyday use and an active lifestyle.
What is 20 ATM?
20 ATM means that the watch is built for more demanding water environments. It can be used for snorkeling, intensive swimming and water sports. This is common on sports watches and diving-inspired models. However, it is important to distinguish between “20 ATM” and professional diving watches that meet specific ISO standards.
What is 30 ATM and more?
30 ATM and above is typical for professional diving watches. These are designed to withstand pressure changes at greater depths and are often equipped with extra seals, a screw-down crown and reinforced case construction. It's not just about the number, but about the entire construction adapted for underwater environments.
What does ATM actually mean on a watch?
ATM stands for atmospheric pressure and is a measure of how much pressure the watch is tested to under controlled conditions. It is important to understand that these tests are done without movement, temperature changes or chemicals such as chlorine and salt. In real-world situations, the pressure can be higher than the stated value. Therefore, you should always choose a higher ATM rating than you think you need if you will be using the watch regularly in water.
How do you choose the right waterproofing?
The choice depends entirely on how the watch will be used. For office environments and everyday life, 3–5 ATM is often sufficient. For swimming and beach life, 10 ATM is a safer option. For more demanding activities in water, 20 ATM or more should be considered. Understanding what 1 ATM, 3 ATM, 5 ATM, 10 ATM, 20 ATM and 30 ATM mean reduces the risk of moisture damage and extends the life of the watch.
