IP and IK ratings explained: how to choose the right protection

When you specify lighting for professional environments, the IP rating and IK rating are two of the most important technical figures. They determine whether a luminaire can handle the physical environment it will sit in, whether that means dust on an industrial floor, rain on a facade or impact in a car park. Choose too little protection and you risk moisture ingress, corrosion and early failure. Choose more than you need and you pay for properties that add no value. This guide clears up what the numbers actually mean and helps you make the right decision already at the design stage.

An incorrect enclosure is rarely spotted immediately. Instead it shows up after a few seasons as condensation behind the glass, corroded contacts or drivers that stop working. The cost then lies not only in the luminaire itself but in labour, access equipment and downtime to replace it. Spending a few extra minutes to understand IP and IK therefore pays off quickly over the life of the installation.

What does the IP rating mean?

IP stands for Ingress Protection and is defined in the standard IEC 60529. The designation consists of the letters IP followed by two digits, for example IP66. The first digit indicates protection against solid objects and dust on a scale from 0 to 6. The second digit indicates protection against water on a scale from 0 to 9. The higher the digit, the better the protection.

A first digit of 6 means the luminaire is completely dust tight, which is standard for outdoor and industrial fittings. The second digit varies more. A 1 handles dripping water, a 5 handles water jets from all directions, and a 6 handles powerful high pressure jets. The digits 7 and 8 cover temporary and continuous immersion in water respectively.

IP65 or IP66: what is the difference?

This is the most common question in practice. Both are completely dust tight. The difference lies in water protection. IP65 handles water jets and is more than enough for most wall mounted outdoor fittings and damp indoor spaces. IP66 handles powerful high pressure jets and is preferable in exposed locations such as coastal facades, wash bays and places where equipment is cleaned with high pressure. For street lighting and stadium floodlights, IP66 is often the standard requirement. See our range of outdoor lighting and street lighting for examples of fittings with the right enclosure.

What does the IK rating mean?

The IK rating indicates mechanical impact resistance according to the standard IEC 62262. The designation is written IK followed by two digits, from IK00 to IK10. The value corresponds to the impact energy in joules that the luminaire withstands without damage. IK08 corresponds to about 5 joules, roughly a half kilo weight falling from 25 centimetres. IK10 corresponds to 20 joules and is used where the risk of damage or vandalism is high.

The IK rating is especially important in car parks, sports halls, tunnels, industrial premises and public spaces where the luminaire may be exposed to knocks, kicks or flying material. A luminaire can have a high IP rating but a low IK rating, so the two values should always be assessed separately.

Reference table for common classes

How to choose the right protection

Start with the environment. If the luminaire will sit outdoors or in a space that is hosed down, work from a minimum of IP65, and IP66 if it is exposed to direct water under pressure. For impact resistance, assess the risk of mechanical contact. In sheltered ceiling mounted positions a lower IK rating is often enough, while wall mounted fittings in public spaces should have IK08 or higher.

• Outdoor and facade: IP65 to IP66, IK08 or higher
• Street, square and parking: IP66, IK10
• Indoor industry and warehouse: IP54 to IP65 depending on dust and cleaning
• Wet areas and wash bays: IP66

Consider temperature and material as well. A high enclosure rating often means a fully sealed luminaire, which affects how heat is carried away. In warm environments you should check the luminaire's stated ambient temperature, often marked ta, so that service life is not affected. In corrosive environments such as coastal sites, swimming pools and food industry, the housing material also matters. Stainless steel, marine grade aluminium or polycarbonate are chosen according to the chemical and mechanical stress the luminaire is exposed to, and complement the protection that the IP and IK values describe.

Remember that the enclosure only holds as long as the luminaire is correctly mounted and sealed. Cable entries, gaskets and glands must be fitted according to the instructions, otherwise the actual protection level drops. See our full product range where IP and IK values are stated for every luminaire, or use our lighting calculator to size the installation correctly from the start.