Sooner or later in many product development projects, someone asks a deceptively simple question: what IP rating do we actually need? Knowing how to choose an IP rating from real operating conditions, rather than from guesswork, is the first step towards a reliable answer. Too often the question comes up late, while a specification sheet is being completed, and the answer becomes a guess dressed up as a decision. A competitor claims IP67, so IP67 goes in the box. It feels safe, but it may be solving the wrong problem.
That kind of guess can be expensive. To choose an IP rating well, begin with the conditions your product will genuinely face, then select the lowest rating that reliably covers them. An IP rating is not a general toughness score. It is the result of two separate ingress protection tests, one for solids and one for water, and specifying a higher number than you need adds sealing cost, complicates assembly and makes servicing harder without making the product any more reliable in the field.
Getting this right early matters, because ingress protection is stubbornly difficult to add late. Sealing reaches into part geometry, material choice, fastener strategy, tooling and assembly sequence. By the time a product reaches tooling, raising a rating is rarely a matter of adding a gasket.
What an IP rating actually means
IP stands for Ingress Protection. The code is defined by the international standard IEC 60529, published by the International Electrotechnical Commission, which classifies how well an enclosure resists the entry of solid objects and water, and how well it stops people reaching hazardous parts inside.
The code takes the form IP followed by two digits:
- First digit (0 to 6): protection against solid foreign objects, dust and contact with hazardous parts.
- Second digit (0 to 9): protection against water.
Those two digits are independent test results, not a combined score. It is the single most useful thing to understand about the system, and it is where most specification errors begin.
The first digit: solids and contact
The first digit runs from 0 to 6. It describes protection against access to hazardous parts and the entry of solid foreign objects. The progression is not simply from “a bit dusty” to “very dusty”. Levels 1 to 4 deal with objects of decreasing size, while levels 5 and 6 deal specifically with dust.
- 0, no protection: no specified protection against contact with hazardous parts or the entry of solid objects.
- 1, objects 50 mm and larger: protection against access with the back of a hand and against large solid objects at least 50 mm across.
- 2, objects 12.5 mm and larger: protection against access with a finger and against objects at least 12.5 mm across.
- 3, objects 2.5 mm and larger: protection against tools, thick wires and similar objects at least 2.5 mm across.
- 4, objects 1 mm and larger: protection against most wires, screws and similar objects at least 1 mm across.
- 5, dust protected: dust may enter, but not in enough quantity to interfere with safe or satisfactory operation.
- 6, dust tight: no dust ingress is permitted.
The difference between 5 and 6 is bigger than one digit suggests. Dust-tight testing can place the enclosure below atmospheric pressure, actively drawing air towards any weak point in the sealing. It is an unforgiving way to find the seam, gland or interface that looked fine in CAD but behaves differently in the real world. For products used around fine conductive dust, grain, quarry fines or construction debris, that distinction can have a direct bearing on reliability.
The second digit: water
The second digit runs from 0 to 9. Each number represents a defined form of water exposure, so the rating should be matched to what the product will actually encounter.
- 0, no protection: no specified protection against water.
- 1, vertically dripping water: protection against vertically falling drops.
- 2, dripping water when tilted: protection against vertically falling drops while the enclosure is tilted by up to 15 degrees.
- 3, spraying water: protection against water sprayed at angles up to 60 degrees from vertical.
- 4, splashing water: protection against water splashed from any direction.
- 5, water jets: protection against water projected by a 6.3 mm nozzle from any direction.
- 6, powerful water jets: protection against stronger jets projected by a 12.5 mm nozzle from any direction.
- 7, temporary immersion: protection during temporary immersion in water, commonly tested at up to 1 metre for 30 minutes.
- 8, continuous immersion: protection during continuous immersion under conditions agreed between the manufacturer and user and stated by the manufacturer.
- 9, high-pressure, high-temperature water jets: protection against close-range jets delivered at high pressure and high temperature.
At first glance this looks like a neat ladder from 0 to 9. It is not quite that simple, which brings us to one of the most common specification mistakes.
The trap that catches most product teams
Here is where the intuition breaks down. The water scale is not a simple ladder. Levels 1 to 6 cover progressively more demanding forms of sprayed or projected water, but immersion is a different physical problem from directed jets, and passing one does not prove the other.
An enclosure rated IP67 has survived temporary immersion. It has not necessarily withstood a pressure washer. A product rated IP69 for high-pressure washdown may still flood if it is dropped in a coolant tank. This is why datasheets for genuinely demanding applications often carry a dual rating, such as IP66 and IP68 declared together. Each claim represents a test that was actually performed.
The letter X trips people up in a similar way. In a code such as IPX4 or IP6X, the X means that characteristic was not declared or not tested. It does not mean zero protection, and it does not mean the product failed. It means you do not have the information, which is a meaningful gap when you are specifying a bought-in component from a supplier.
How to choose an IP rating in five steps
The rating should be an output of your requirements work, not an input copied from a competitor product or a previous project. To choose an IP rating with confidence, begin with evidence about the environment, intended use and complete product lifecycle.
1. Describe the real environment, not the category
When you choose an IP rating, start by writing down what will actually reach the product. Rain while mounted vertically is a different problem from a hose aimed at a seam. Occasional splash in a workshop is not daily washdown in a food processing facility. Dust in an office is not airborne fines in a grain shed. Include how the product sits in use, because water striking a vertical face behaves very differently from water pooling on a horizontal surface or gathering around a top-mounted cable entry.
2. Include the whole product lifecycle
Consider transport, storage, installation, cleaning and servicing, not just normal operation. Ingress failures can occur during cleaning or after an enclosure has been reopened and the gasket has not been re-seated correctly. If the product will be opened in the field, its sealing must tolerate repeated assembly in real working conditions.
3. Separate the solids requirement from the water requirement
Because the digits are independent, decide each one on its own evidence. Plenty of products genuinely need IP6X for dust because of where they live, while needing only IPX4 for water because they never meet jets or immersion. Specifying IP65 when IP64 would do can mean redesigning seals and adding assembly steps for a condition the product will never encounter.
4. Test the specification against cost and manufacture
Every step up the scale has consequences that shape the product and the production line. Higher ratings typically call for continuous gasket paths, controlled compression, tighter tolerances on sealing faces, more fasteners, sealed connectors and glands, and sometimes ultrasonic welding or bonding in place of serviceable joints. Material and finish selection narrows as sealing demands rise, particularly where gasket compatibility, UV exposure or cleaning chemicals are involved. The assembly itself matters just as much: our guide to Design for Assembly (DFA) explains how part count, fastening, access and error-proofing influence production quality and consistency. Venting becomes a design problem in its own right, because a sealed enclosure that heats and cools will breathe, and a breathable membrane is often the right answer where a fully sealed box is not.
5. Design for the test, then verify
Once you choose an IP rating, treat it as a performance claim that must be verified. An IP rating is declared by test, not by inspection or calculation. If the specification matters commercially, plan the verification early: which laboratory, which sample configuration, which production-representative parts, and at what point in the programme. Rating a product on the strength of a CAD review is how teams discover sealing problems after tooling has been cut.
What an IP rating does not tell you
The IP code has a defined scope, and several real-world risks sit outside it entirely. IEC 60529 does not address corrosion, icing, oil or coolant exposure, hazardous atmospheres, or mechanical impact. Impact resistance is covered separately by the IK code.
For durable products and outdoor equipment, these omissions matter. A coastal installation needs a strategy for salt exposure that no IP number describes, while a site tool needs impact resistance that IP66 says nothing about. UV stability, chemical compatibility and thermal cycling also sit outside the code.
It is also worth remembering that the rating applies to the configuration that was tested. The finished product includes buttons, seals, displays, connectors, cable glands, fasteners and any holes added later. A beautifully sealed housing with a poorly chosen or poorly fitted gland is still an unsealed product. This is one reason ingress protection belongs in the conversation from the earliest stages of enclosure design for electronics, where sealing, thermal management and aesthetics all compete for the same geometry.
Common questions about choosing an IP rating
Is IP68 always better than IP67?
For immersion, IPX8 represents protection under conditions specified by the manufacturer, while IPX7 covers temporary immersion under defined test conditions. Neither rating establishes performance against a high-pressure water jet, which is a separate test. The more appropriate rating depends on the exposure you are designing for.
What does IPX4 mean?
It means the product is protected against splashing water from any direction, and that solids protection was not declared or not tested. The X is an absence of information rather than an absence of protection.
Can you improve an IP rating after the design is complete?
Sometimes, but it is usually expensive. Sealing affects part geometry, tooling, material choice and assembly method, so raising a rating late often means tooling modifications. This is exactly the kind of requirement worth resolving before a design freeze, while changes still cost hours rather than tooling.
Do I need an IP rating at all?
Not every product does. If yours lives indoors, is never cleaned with liquid and faces no meaningful dust, a declared rating may add testing cost without commercial benefit. The real question is whether the rating serves a genuine requirement: a customer expectation, a tender condition, or a regulatory obligation.
Treat ingress protection as a design decision
The best answer is not automatically the biggest number on the datasheet. The aim is to choose an IP rating that reflects genuine exposure and can be designed, manufactured and verified with confidence. Reliable products result from deliberate requirements and sound engineering, not from selecting the highest available number as a precaution.
In practice that means bringing ingress requirements into the room early, alongside material selection, assembly strategy and manufacturing method, and carrying them through to production where sealing performance is confirmed on production-representative parts rather than on prototypes. It is a core consideration in our approach to enclosure design, where protection, performance and manufacturability are resolved together rather than in sequence.
If you are weighing up an ingress requirement for a new product, or you have one already in the field that is letting water or dust in, we are always happy to talk it through. Get in touch with the team at Whistle Design Group and we can work through the environment, a realistic rating and the design and verification path before you commit to tooling.