What do IP ratings like IP67 and IP68 actually mean?
IP stands for Ingress Protection, and the two digits rate protection against solids and liquids separately, under the international standard IEC 60529.
The first digit — solids, on a scale of 0 to 6:
5 — dust protected; some dust may enter but not enough to interfere.
6 — dust tight; no ingress at all. Almost all modern phones rated at all achieve 6.
The second digit — liquids, on a scale of 0 to 9:
4 — splashing water from any direction.
5 — low-pressure water jets.
6 — powerful water jets.
7 — immersion in 1 metre of water for 30 minutes.
8 — immersion beyond 1 metre, to a depth and duration specified by the manufacturer. This is the crucial detail: IP68 is not a fixed standard. One device's IP68 may mean 1.5m for 30 minutes and another's 6m for an hour. You must read the manufacturer's stated conditions.
9K — high-pressure, high-temperature jets, common on industrial and automotive equipment.
An X means not tested. IPX4 has no solids rating; IP6X has no liquids rating. It does not mean zero protection, only that it was not assessed.
The counterintuitive part: the scale is not strictly cumulative between 6 and 7. A device tested for immersion has not necessarily been tested against pressurised jets, which is why some equipment carries a dual rating like IP66/IP68.
What the ratings do not cover, and this matters most practically:
Testing uses fresh, still water at controlled temperature. Saltwater, chlorinated pools, soap, coffee and pressurised taps are all outside the test.
Ratings degrade. Seals age, and a drop can compromise them invisibly.
Warranties routinely exclude liquid damage regardless of the IP rating, which surprises people who assumed the rating was a guarantee.