IP stands for Ingress Protection, and the two digits after it each tell you something specific. The first digit rates protection against solid particles on a scale of 0 to 6. The second rates protection against liquids on a scale of 0 to 9. So IP65 means fully dust-tight and protected against low-pressure water jets from any direction.

A common point of confusion is that a higher liquid rating does not always include lower ones. IP67 covers temporary immersion up to 1 meter, but that does not automatically mean the enclosure handles sustained water jets as well as an IP65 unit would. If your application involves both, look for a dual-rated enclosure or confirm with the manufacturer.

For practical selection, start with the environment. Outdoor electrical cabinets in washdown areas typically need IP65 or IP66. Submersible sensors or connectors in water treatment usually call for IP67 or IP68, with the specific depth and duration negotiated with the supplier. Indoor control panels in clean environments can often get by with IP54.

One thing worth checking on the datasheet is whether the rating was tested with the cable glands and connectors installed. An enclosure body might be rated IP67, but the assembly as shipped could be a different story.

IP Ratings for Enclosures: What the Numbers Actually Mean