The IP rating (International Protection) is used to detemine the degree of protection provided by an enclosure. It is a standard maintained by IEC 60529. The IP rating is made up of 2 digits. It may have additional letter if the actual personal protection is better than that indicated by the first digit.

First Digit:
0 Unprotected
1 Protect against object with a diameter 50mm or more
2 Protect against object with a diameter 12.5mm or more
3 Protect against object with a diameter 2.5mm or more
4 Protect against object with a diameter 1mm or more
5 Protect against dust
6 Dust proof

Second Digit:
0 Unprotected
1 Protect against water falling vertically
2 Protect against water falling up to 15°C from vertical
3 Protect against water falling up to 60°C from vertical
4 Protect against splasing of water from any directions
5 Protect against water jets from any directions
6 Protect against power water jets from any directions
7 Protect against temporary immersions in water
8 Protect against continuous immersions in water

Additional Letter:
A Protect against access with the back of the hand
B Protected against accesswith a finger
C Protected against accesswith a tool
D Protected against accesswith a wire

Supplementary Letter:
H High-voltage apparatus
M Tested for harmful effects due to the ingress of water when the movable parts of the equipment (for example, the rotor of a rotating machine) are in motion
S Tested for harmful effects due to the ingress of water when the movable parts of the equipment (for example, the rotor of a rotating machine) are stationary
W Suitable for use under specified weather conditions and provided with additional protective features or processes