How to Replace a 16×25×1 Furnace Filter
16×25×1 is one of the most common disposable furnace filter sizes. Changing it takes under five minutes and is the highest-ROI maintenance task for airflow, dust, and coil cleanliness.
Updated July 2026 · 3 min read · Canada
Symptoms
- Visible gray media
- Rising dust on vents
- Louder blower or longer heat cycles
Likely causes
- Loaded filter media
- Skipped monthly/seasonal changes
What to do
1. Locate the filter slot
Usually in the return grille, in a slot at the furnace cabinet, or in the air handler above a basement unit.
2. Slide out the old 16×25×1
Note the airflow arrow direction. Vacuum loose dust from the slot so it does not fall into the blower.
3. Insert the new filter with arrow toward the blower
Arrow points in the direction of airflow (toward the furnace). Seat it fully so air cannot bypass around the edges.
Stop and call a pro when
- You find water, rust, or biological growth in the slot
- The cabinet size is not actually 16×25×1 despite an old filter that size
Related guides
- Filter Size Guide — How to read furnace filter dimensions, why nominal vs. actual sizes differ, and which MERV rating to buy without starving airflow.
- Replace 20×25×1 Filter — Step-by-step 20x25x1 furnace filter replacement with MERV tips and multipack product links for the exact size.
- Replace 16×20×1 Filter — 16x20x1 filter replacement guide for closet air handlers and shorter return slots, with size-check tips vs 16×25.
- Aprilaire 213 Replacement — How to replace an Aprilaire 213 media filter in 2210/4200/2200-series air cleaners, including orientation and change intervals.
- Replace 18×24×1 Filter — Replace an 18x24x1 furnace or return filter — a mid-width size often misread as 16×25 — with MERV guidance and buy links.
FAQ
How often should I change a 16×25×1?
Every 30–90 days depending on pets, construction dust, and runtime. Check monthly during heavy heating or cooling seasons.
Need a licensed tech instead?
If the guide says to stop — or the part swap did not clear the fault — get free quotes from licensed local HVAC contractors.
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