The IP code or ingress protection code indicates how well a device is protected against water and dust. It is defined by the International Electrotechnical Commission (IEC) under the international standard IEC 60529 which classifies and provides a guideline to the degree of protection provided by mechanical casings and electrical enclosures against intrusion, dust, accidental contact, and water. It is published in the European Union by the European Committee for Electrotechnical Standardization (CENELEC) as EN 60529.

The standard aims to provide users more detailed information than vague marketing terms such as waterproof. For example, a cellular phone rated at IP67 is "dust resistant" and can be "immersed in 1 meter of freshwater for up to 30 minutes". Similarly, an electrical socket rated IP22 is protected against insertion of fingers and will not become unsafe during a specified test in which it is exposed to vertically or nearly vertically dripping water. IP22 or IP2X are typical minimum requirements for the design of electrical accessories for indoor use.

The digits indicate conformity with the conditions summarized in the tables below. The digit 0 is used where no protection is provided. The digit is replaced with the letter X when insufficient data has been gathered to assign a protection level. The device can become less capable; however, it cannot become unsafe.

There are no hyphens in a standard IP code. IPX-8 (for example) is thus an invalid IP code.^[1]

In the original IEC 60529 standard from year 1976, the letters IP are used without providing an explanation, and referred as "characteristic letters".^[2] In the next editions of the standard, from years 1989 and 1999 respectively, the IP is explained to denote "international protection" on both French and English pages. According to the Finnish national committee of the IEC, one possibility is that the abbreviation is a combination of English word ingress and French word pénétration which stands for ingress, but finding the correct answer would require doing a historical study on the 1970's standardization, which is difficult because the experts preparing the original standards are probably retired or deceased.^[3]

This table shows what each digit or part of the IP code represents.^[4]

DIN 40050-9 extended the newer IEC 60529 rating system with an IP69K rating for high-pressure, high-temperature wash-down applications.^[7] Enclosures conforming with ISO 20653:2013 must be both dust-tight (IP6X) and able to withstand high-pressure and steam cleaning.

The IPx9K standard was originally developed for road vehicles—especially those that need regular intensive cleaning (dump trucks, concrete mixers, etc.)—but it also finds use in other areas, such as food processing machinery and car wash systems. It was superseded by ISO 20653:2013 Road Vehicles-Degrees of protection (IP code),^[8] and complemented by the addition of a level 9 water ingress testing to IEC 60529, which includes essentially the same spray test as IPx9K, but also includes, in Figure 10 of the standard, a drawing for a test fixture designed to verify the correct water pressure.

In the U.S., the National Electrical Manufacturers Association defines NEMA enclosure types in NEMA standard number 250. The following table outlines which IEC 60529 IP code each respective NEMA guideline meets. Ratings between the two standards are not directly equivalent: NEMA ratings also require additional product features and tests (such as functionality under icing conditions, enclosures for hazardous areas, knock-outs for cable connections and others) not addressed by IP ratings.

• Appliance classes
• EN 62262 – IK code on resistance to mechanical impacts
• MIL-STD-810
• U.S. Military connector specifications for military equivalents
• Water Resistant mark on wrist watches