IP51 vs IP66
Head-to-head comparison of two IEC 60529 ingress protection ratings.
IP51 and IP66 are both IEC 60529 ingress protection codes, but they differ in solid-object protection (level 5 vs 6) and liquid protection (level 1 vs 6). IP51 is rated for dust-protected and vertically dripping water, while IP66 provides dust-tight and powerful water jets (12.5 mm nozzle).
With IP51, an enclosure receives dust-protected (limited ingress, no harmful deposit) and protection against vertically falling drops of water. Dripping water shall have no harmful effects.. It is an IEC 60529 ingress protection code combining first-digit (solid) level 5 with second-digit (liquid) level 1.
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)
IP51
5 — Dust-Protected
IP66
6 — Dust-Tight
Liquid protection (second digit)
IP51
1 — Vertically Dripping Water
IP66
6 — Powerful Water Jets (12.5 mm nozzle)
Dust-tight
IP51
Limited
IP66
Yes
Water-jet resistant
IP51
No
IP66
Yes
Submersible
IP51
No
IP66
No
Outdoor suitable
IP51
No
IP66
Yes
The exact difference (IP51 vs IP66)
Solid protection
IP51
Level 5 — Dust-Protected
IP66
Level 6 — Dust-Tight
IP51 provides "Dust-Protected" (level 5), while IP66 provides "Dust-Tight" (level 6). IP66 is 1 level higher.
Liquid protection
IP51
Level 1 — Vertically Dripping Water
IP66
Level 6 — Powerful Water Jets (12.5 mm nozzle)
IP51 handles 0.1 mm/min drip rate (Vertically Dripping Water), while IP66 handles 100 kPa (Powerful Water Jets (12.5 mm nozzle)). IP66 provides 5 levels more liquid protection.
NEMA equivalents
No direct NEMA equivalent.
Recommendation
IP66 offers higher overall protection than IP51. Choose IP66 for harsher environments; IP51 may suffice for milder conditions and can be more cost-effective.