IP40 vs IP66
Head-to-head comparison of two IEC 60529 ingress protection ratings.
IP40 and IP66 are both IEC 60529 ingress protection codes, but they differ in solid-object protection (level 4 vs 6) and liquid protection (level 0 vs 6). IP40 is rated for > 1 mm — small wires and no protection, while IP66 provides dust-tight and powerful water jets (12.5 mm nozzle).
IP40 protects against small tools and wires (1 mm objects) but offers no water protection. Useful for indoor equipment needing finer ingress protection against small debris and tools.
IP66 is dust-tight and resists powerful water jets (12.5 mm nozzle, 100 kPa). A robust outdoor rating for equipment exposed to heavy rain, storms, or directed high-pressure hosing (but not high-pressure washdown).
Detailed comparison
The stronger rating on each row is highlighted in emerald.
Solid protection (first digit)
IP40
4 — > 1 mm — Small Wires
IP66
6 — Dust-Tight
Liquid protection (second digit)
IP40
0 — No Protection
IP66
6 — Powerful Water Jets (12.5 mm nozzle)
Dust-tight
IP40
No
IP66
Yes
Water-jet resistant
IP40
No
IP66
Yes
Submersible
IP40
No
IP66
No
Outdoor suitable
IP40
No
IP66
Yes
The exact difference (IP40 vs IP66)
Solid protection
IP40
Level 4 — > 1 mm — Small Wires
IP66
Level 6 — Dust-Tight
IP40 provides "> 1 mm — Small Wires" (level 4), while IP66 provides "Dust-Tight" (level 6). IP66 is 2 levels higher.
Liquid protection
IP40
Level 0 — No Protection
IP66
Level 6 — Powerful Water Jets (12.5 mm nozzle)
IP40 provides "No Protection" (level 0), while IP66 provides "Powerful Water Jets (12.5 mm nozzle)" (level 6). IP66 is 6 levels higher.
NEMA equivalents
No direct NEMA equivalent.
Recommendation
IP66 offers higher overall protection than IP40. Choose IP66 for harsher environments; IP40 may suffice for milder conditions and can be more cost-effective.