18x18 · Furnace & AC Filter

18x18 air filter — every MERV & depth

The 18x18 is one of the most common US furnace and return-grille sizes. A 1" filter measures about 17.5 × 17.5 × 0.75 in actual. Pick your depth and MERV rating below — higher MERV filters finer particles, so match it to your household.

18x18x1 — 1" depth

Change every 60–90 days. Set a reminder so airflow never drops.

18x18x1 · MERV 8 — Standard protectionfrom $7.23 →18x18x1 · MERV 11 — Allergy & petfrom $10.00 →18x18x1 · MERV 13 — Maximum filtrationfrom $12.78 →

18x18x2 — 2" depth

Change every 3 months. Set a reminder so airflow never drops.

18x18x2 · MERV 8 — Standard protectionfrom $10.56 →18x18x2 · MERV 11 — Allergy & petfrom $13.34 →18x18x2 · MERV 13 — Maximum filtrationfrom $16.12 →

18x18x4 — 4" depth

Change every 6–12 months. Deep media filters last far longer between changes.

18x18x4 · MERV 8 — Standard protectionfrom $17.23 →18x18x4 · MERV 11 — Allergy & petfrom $20.01 →18x18x4 · MERV 13 — Maximum filtrationfrom $22.79 →

Not sure which MERV?

MERV 8

Standard protection

Best for everyday home use — the standard choice to protect your HVAC system.

MERV 11

Allergy & pet

Best for homes with pets or mild allergies.

MERV 13

Maximum filtration

Best for allergy and asthma sufferers, and homes dealing with wildfire smoke.

MERV 8 vs 11 →MERV 11 vs 13 →MERV 8 vs 13 →

← All air filter sizes