What is an IP rating?

Glossary · Alarms, lighting and home installs

How an IP rating works

IP stands for ingress protection. The rating tells you how well a fitting, light or appliance keeps dust and water out.^{[1]NICEIC, Bathrooms and electrics: what you need to know} It is a code of the letters IP followed by two digits. The first digit is the resistance to solids such as dust and the second is the resistance to water. A 0 means no protection, and higher numbers mean a higher level of protection.^{[1]NICEIC, Bathrooms and electrics: what you need to know}

Sometimes you only see one number, such as IPX4. The letter X replaces a digit that is not stated, so IPX4 describes the water protection only. NICEIC says some makers list two numbers for bathroom equipment, as in IP44, to show both dust and water resistance.^{[1]NICEIC, Bathrooms and electrics: what you need to know}

For water, NICEIC says the rating runs from IPX0, negligible water resistance, to IPX8, fully waterproof and able to withstand indefinite submersion.^{[1]NICEIC, Bathrooms and electrics: what you need to know} The ratings householders meet most often are in the table below.

The ratings you will meet

The meanings and the bathroom uses in the table are from NICEIC.^{[1]NICEIC, Bathrooms and electrics: what you need to know} The IET confirms the zone 1 and zone 2 requirement, saying Section 701 requires electrical equipment in zones 1 and 2 to have a degree of protection of at least IPX4.^{[3]IET, Section 701 - Locations containing a bath or shower} Our page on bathroom zones explains where the zones are.

Outdoors, Electrical Safety First says to consider the area to be lit, the power source and the IP rating, and to make sure outdoor lights are weatherproof.^{[4]Electrical Safety First, Electrical safety advice for outdoor lighting} The same advice says mains outdoor lighting should be installed by a registered electrician in line with the manufacturer’s instructions and BS 7671.^{[4]Electrical Safety First, Electrical safety advice for outdoor lighting}

Example

Fatima in Chapel Allerton is replacing the light over her bath. The new fitting is in zone 1, so it needs a rating of at least IPX4.^{[2]IET, EICR myths (Wiring Matters)} She finds a fitting marked IP44, which gives both the dust and the water rating and meets the bathroom minimum.^{[1]NICEIC, Bathrooms and electrics: what you need to know} Because the light is in a bathroom zone, the work is for a registered electrician.

Her neighbour Ben wants a PIR sensor floodlight on the side of his house. He checks the box for an IP rating and makes sure the light is marked weatherproof before he buys.^{[4]Electrical Safety First, Electrical safety advice for outdoor lighting} The fitting and wiring are done by a registered electrician. Our security lighting service wires outdoor lights to a dedicated weatherproof outdoor circuit.^{[5]Martin Day Electricians, Security lighting installation in Leeds}

What people get wrong

A common belief is that a bathroom light must be IP65. It does not. The minimum rating for a light in zone 1 of a room with a bath or shower is IPX4, protection against splashing water.

That comes from the IET’s guidance on EICR myths, which names the IP65 belief directly.^{[2]IET, EICR myths (Wiring Matters)} The other mistake is assuming a higher number is always needed. A higher rating is not wrong, but it is not required in every location. The rating needed depends on where the equipment sits. Where equipment may face water jets, a higher level may be required, which is what IPX5 covers.^{[1]NICEIC, Bathrooms and electrics: what you need to know}

The bottom line

An IP rating is a two-digit code that tells you how well a fitting resists dust and water, with higher numbers meaning more protection and an X meaning that digit is not stated. IPX4 is the minimum in bathroom zones 1 and 2, and outdoor equipment must be weatherproof. Check the rating before you buy, and leave any bathroom or outdoor installation to a registered electrician.