Filter size & MERV helper
What this is: A quick guide to picking a replacement furnace/air-handler filter — first the size stamped on the old one, then a MERV rating your blower can usually handle.
When to use it: You’re standing in the filter aisle, or shopping online, and you’re not sure whether “higher MERV = better” is safe for your system.
How to use the inputs:
- Pull the old filter (power off if you prefer) and read the size printed on the frame (e.g. 16x25x1).
- Choose that size below — or “I still need to check” if you haven’t looked yet.
- Pick the MERV you’re considering. Tick the boxes if you have pets/dust or if past “high MERV” filters made airflow feel weak.
How to read the result: Treat it as plain-English guidance, not a lab rating. “Size first” always wins — a wrong size leaks dirty air around the filter.
Safety limits: Don’t force a very high MERV into a system that already feels starved for air. Don’t open sealed cabinets beyond the filter slot. If airflow worsens, ice forms, or the system short-cycles after a change, go back to a lower MERV and call a tech if it continues.