The IP rating or ingress protection code is defined by the International Electrotechnical Commission (IEC). It classifies and provides a guideline to the degree of protection provided by casings and enclosures against intrusion of dust and contact with water.
IP
| The first digit indicates the level of protection that the enclosure provides against access to solid parts. |
| The second digit indicates the level of protection that the enclosure provides against harmful ingress of water. |
| First Number Rating | |
|---|---|
| X | Means there is no data available to specify a IP rating with regard to this criterion. |
| 0 |  No protection against contact and ingress of objects. |
| 1 |  Any large surface of the body, such as the back of a hand, but no protection against deliberate contact with a body part. Protection from solid objects over 50mm in diameter. |
| 2 |  Fingers or similar objects. Protection from solid objects over 12.5mm in diameter. |
| 3 |  Tools, thick wires, etc. Protection from solid objects over 2.5mm in diameter. |
| 4 |  Most wires, slender screws, large ants etc. Protection from solid objects over 1mm in diameter. |
| 5 |  Ingress of dust is not entirely prevented, but it must not enter in sufficient quantity to interfere with the safe operation of the equipment. |
| 6 | No ingress of dust; complete protection against contact (dust-tight). |
| Second Number Rating | |
|---|---|
| X | Means there is no data available to specify a IP rating with regard to this criterion. |
| 0 | No protection against ingress of liquid. |
| 1 |  Dripping water (vertically falling drops) shall have no unsafe effect on the enclosure. |
| 2 |  Vertically dripping water shall have no harmful effect when the enclosure is tilted at an angle of 15° from its normal position. |
| 3 |  Water falling as a spray at any angle up to 60° from the vertical shall have no harmful effect. |
| 4 |  Water splashing against the enclosure from any direction shall have no harmful effect |
| 5 |  Water projected by a nozzle (6.3 mm) against enclosure from any direction shall have no harmful effects. |
| 6 | Water projected in powerful jets (12.5 mm) against the enclosure from any direction shall have no harmful effects. |
| 7 |  Ingress of water in harmful quantity shall not be possible when the enclosure is immersed in water under defined conditions of pressure and time (up to 1 meter). |
| 8 | The equipment is suitable for continuous immersion in water under conditions which shall be specified by the manufacturer. |
| 9K |  Protected against close-range high pressure, high-temperature spray downs. |
Additional letter (optional)
For the protection of personnel against access to hazardous parts with:
| Letter | Meaning |
|---|---|
| A | Back of hand |
| B | Finger |
| C | Tool |
| D | Wire |
Supplementary letter (optional)
For the protection of equipment specific to:
| Letter | Meaning |
|---|---|
| F | Oil resistant |
| H | High voltage apparatus |
| M | Motion during water test |
| S | Stationary during water test |
| W | Weather conditions |
For additional information and further reading see wikipedia