IP numbers are often quoted on enclosures, connectors etc to indicate protection from solids, liquids and impact. The table below gives a description of these ratings. Note that the third number, protection against impacts, is often omitted.
| IP # | First Number - Protection against solids | Second Number - Protection against liquids | Third Number - Protection against mechanical impacts (often omitted) |
| 0 | No Protection | No Protection | No Protection |
| 1 | Protected against solid objects over 50mm | Protected against vertically falling drops of water | Protected against impact of 0.225 joules |
| 2 | Protected against solid objects over 12mm | Protected against direct sprays up to 15 deg. from vertical | Protected against impact of 0.375 joules |
| 3 | Protected against solid objects over 2.5mm | Protected against direct sprays up to 60 deg. from vertical | Protected against impact of 0.5 joules |
| 4 | Protected against solid objects over 1mm | Protected against direct sprays from all directions - limited ingress permitted | Protected against impact of 2.0 joules |
| 5 | Protected against dust - limited ingress permitted | Protected against low pressure jets from all directions - limited ingress permitted | Protected against impact of 6.0 joules |
| 6 | Totally protected against dust | Protected against strong jets from all directions - limited ingress permitted | Protected against impact of 20.0 joules |
| 7 | | Protected against effects of immersion from 15cm - 1m | |
| 8 | | Protected against long periods of immersion under pressure | |
