The IP rating (Ingress Protection) is one of the most important figures when choosing an electrical enclosure or box. It defines how well the enclosure protects against the ingress of solid objects and water. Understanding it avoids failures, downtime and the extra cost of over- or under-specifying. This definitive guide explains, step by step, what each digit of the IP code means, the most common ratings (IP54, IP65, IP66, IP67, IP68, IP69K) and how to choose the right one for each installation.
How to read an IP code: anatomy of “IPXY”
A full IP code is made up of the fixed letters IP and two characteristic digits. Each measures something different and they are independent of each other:
Protection
61st digit
SOLIDS
(0–6)
52nd digit
LIQUIDS
(0–9K)
Koptional
letter
When a digit is not tested or not relevant, it is replaced by an X (for example, IPX7 means only protection against water has been assessed). The higher the number, the greater the protection. A common mistake is to think that “more is always better”: a higher rating than needed makes the enclosure more expensive without adding value.
First digit: protection against solids and dust (0–6)
The first digit indicates protection against contact with hazardous parts and against the ingress of foreign solid objects, from large objects to the finest dust:
| Digit | Protection against solids | Practical meaning |
|---|---|---|
| 0 | No protection | No protection against contact or objects |
| 1 | Objects ≥ 50 mm | Accidental contact with the back of the hand |
| 2 | Objects ≥ 12.5 mm | Fingers or similar objects |
| 3 | Objects ≥ 2.5 mm | Tools, thick wires |
| 4 | Objects ≥ 1 mm | Wires, screws, thin cables |
| 5 | Dust protected | Some dust enters, but not in a harmful amount |
| 6 | Dust tight | No dust ingress (hermetic) |
Second digit: protection against liquids (0–9K)
The second digit indicates protection against the ingress of water, from vertical dripping to cleaning with high-pressure, high-temperature water:
| Digit | Protection against water | Test / situation |
|---|---|---|
| 0 | No protection | — |
| 1 | Vertical dripping | Condensation, dripping from above |
| 2 | Dripping at 15° tilt | Dripping with the enclosure slightly tilted |
| 3 | Spraying water (rain) | Spray up to 60° from vertical |
| 4 | Splashing water | Splashes from any direction |
| 5 | Water jets | Hose with a 6.3 mm nozzle |
| 6 | Powerful jets | Hose with a 12.5 mm nozzle (heavy seas) |
| 7 | Temporary immersion | Up to 1 m deep, 30 minutes |
| 8 | Continuous immersion | Over 1 m, under conditions defined by the manufacturer |
| 9 / 9K | High-pressure, high-temperature cleaning | Water at ~80 °C and 80–100 bar (industrial washdown) |
Additional letters of the IP code (optional)
Besides the two digits, the IEC 60529 standard provides optional letters that rarely appear, but are worth knowing:
- Additional letters (A, B, C, D): indicate the degree of protection of people against access to hazardous parts (back of the hand, finger, tool, wire).
- Supplementary letters (H, M, S, W): H = high-voltage apparatus; M = tested against water while in motion; S = tested while stationary; W = protected against specific weather conditions.
The most common IP ratings and what they mean
In practice, most enclosures and boxes fall into a few ratings. These are the most requested:
IP54
Dust protected and resistant to splashing water. General indoor use and light industry.
IP55
Dust and water jets. Demanding indoor and sheltered outdoor use.
IP65
Dust tight and jet resistant. The standard for many industrial and outdoor environments.
IP66
Dust tight and resistant to powerful jets. Outdoor, coastal, frequent washdowns.
IP67
Dust tight and resistant to temporary immersion (1 m, 30 min). Flood-prone areas.
IP68
Dust tight and continuous immersion. Submerged or very severe applications.
IP69 / IP69K
Dust tight and high-pressure, high-temperature cleaning. Food and pharmaceutical industry.
IP65 vs IP66 vs IP67 vs IP68: key differences
This is the most frequent question. They all share the 6 for “dust tight”; what changes is the protection against water:
| Rating | Water | When to choose it |
|---|---|---|
| IP65 | Water jets (6.3 mm) | Industrial indoors, outdoors with rain and gentle cleaning hoses |
| IP66 | Powerful jets (12.5 mm) | Severe outdoor, marine environments, moderate pressure washdowns |
| IP67 | Temporary immersion 1 m | Risk of occasional flooding or being briefly submerged |
| IP68 | Continuous immersion >1 m | Permanently submerged equipment or extreme conditions |
IP and NEMA equivalence
In international projects (especially with US customers) the NEMA classification appears. It is not an exact equivalence —NEMA also assesses corrosion, ice or oil— but this guideline table helps. Important: the conversion goes from NEMA to IP, not the other way round.
| NEMA | Approx. IP | Typical use |
|---|---|---|
| NEMA 1 | IP10 | Indoor, accidental contact |
| NEMA 3R | IP14 | Outdoor, rain and ice formation |
| NEMA 12 | IP52 | Industrial indoor, dust and dripping |
| NEMA 4 / 4X | IP66 | Outdoor, jets; 4X adds corrosion resistance (stainless) |
| NEMA 6 | IP67 | Temporary immersion |
| NEMA 6P | IP68 | Prolonged immersion |
IP is not the same as IK: be careful
A common mistake is to confuse the IP rating with the IK rating. IK (standard EN 62262) measures the resistance to mechanical impact of the enclosure, on a scale from IK00 to IK10 (0 to 20 joules of impact energy). An enclosure can be IP66 but have a low IK, or vice versa. In environments with a risk of impact or vandalism (public areas, heavy industry) you must specify both: for example, IP66 IK10.
How to choose the IP rating for your enclosure
The golden rule: choose the IP rating according to the actual installation environment, no more and no less. This is our practical recommendation:
| Environment | Recommended IP rating | Delvalle solution |
|---|---|---|
| Clean indoor (office, technical room) | IP41–IP54 | Indoor enclosures |
| Industrial indoor (dust, splashes) | IP54–IP55 | Industrial enclosures |
| Outdoor | IP65–IP66 | Outdoor enclosures |
| Food / pharmaceutical (pressure washdown) | IP66 / IP69K | Hygienic stainless enclosures |
| Flood-prone or submerged areas | IP67–IP68 | IP68 watertight enclosures |
Remember that the IP rating goes hand in hand with the material and finish: in corrosive environments a high IP is not enough, you also need the right stainless steel. We explain it in our guide on ISO 12944 corrosivity categories.