Furnace Filter Size Chart: Find Your Exact AC & HVAC Filter Size (2025 Guide)
Quick Filter Size Finder - Most Popular Sizes
Click your filter size below to shop our best-selling filters with FREE shipping on 6-packs:
Important: Nominal vs Actual Filter Sizes
Before you buy: Furnace filters have two sizes - Nominal (like 16x25x1) printed on the frame, and Actual (like 15.5x24.5x0.75) which are the true measurements. Always check both sizes when switching brands to ensure a perfect fit. Learn more about nominal vs actual sizes →
Standard Furnace Filter Sizes - Quick Reference Chart
Find your furnace filter size, AC filter size, or HVAC filter size in seconds. All filters are Made in USA with quality synthetic materials.
| Popular Size | Actual Dimensions | Best For | Shop Now |
|---|---|---|---|
| 16x25x1 | 15.5" × 24.5" × 0.75" | Most homes, standard systems | Get MERV 13 → |
| 20x20x1 | 19.5" × 19.5" × 0.75" | Square returns, older systems | Shop 6-Pack → |
| 16x20x1 | 15.5" × 19.5" × 0.75" | Smaller HVAC systems | Get MERV 13 → |
| 20x25x1 | 19.5" × 24.5" × 0.75" | Large residential systems | Shop Now → |
| 24x24x1 | 23.375" × 23.375" × 0.75" | Commercial, large homes | View Options → |
Complete Furnace Filter Size Chart - All Standard Sizes
Browse our complete inventory of 1 inch furnace filters (actual thickness 0.75"). Click any size to shop filters in MERV 8, MERV 11, or MERV 13 ratings.
Filter Collections by Depth: 1" Deep Filters | 2" Deep Filters | 4" Deep Filters
| Furnace Filter Size (Nominal) | Actual Size |
| 10x10x1 | 9.5 x 9.5 x .75 |
| 10x20x1 | 9.5 x 19.5 x .75 |
| 12x12x1 | 11.75 x 11.75 x .75 |
| 12x20x1 | 11.5 x 19.5 x .75 |
| 14x20x1 | 13.5 x 19.5 x .75 |
| 14x25x1 | 13.5 x 24.5 x .75 |
| 15x20x1 | 14.5 x 19.5 x .75 |
| 16x20x1 | 15.5 x 19.5 x .75 |
| 16x25x1 | 15.5 x 24.5 x .75 |
| 18x24x1 | 17.375 x 23.375 x .75 |
| 20x20x1 | 19.5 x 19.5 x .75 |
| 20x25x1 | 19.5 x 24.5 x .75 |
| 20x30x1 | 19.5 x 29.5 x .75 |
| 24x24x1 | 23.375 x 23.375 x .75 |
| 24x30x1 | 23.5 x 29.5 x .75 |
| 25x25x1 | 24.5 x 24.5 x .75 |
View Complete List of All Filter Sizes →
Understanding MERV Ratings for Your Furnace Filter
MERV (Minimum Efficiency Reporting Value) ratings help you choose the right filter for your needs:
| MERV Rating | Best For | Filters Out | Shop Filters |
|---|---|---|---|
| MERV 8 | Basic home protection | Dust, pollen, dust mites | Shop MERV 8 → |
| MERV 11 | Allergy relief | Pet dander, mold spores, fine dust | Shop MERV 11 → |
| MERV 13 | Maximum filtration | Bacteria, smoke, virus carriers | Shop MERV 13 → |
Ready for Cleaner Air?
Upgrade to MERV 13 filters for maximum protection against allergens and pollutants
Browse MERV 13 Filters →Find Your Furnace Filter by Brand
Shop filters for specific HVAC brands. Click your brand to see all compatible sizes and models:
| Brand | Popular Models | Shop Brand |
| Lennox | X6672, X6675, X8788 | Shop Lennox → |
| Carrier/Bryant | FILXXCAR0016, FILXXCAR0020 | Shop Carrier → |
| Honeywell | FC100A1003, FC100A1029 | Shop Honeywell → |
| Aprilaire | Various models | Shop Aprilaire → |
| Totaline | P102-1620, P102-2025 | Shop Totaline → |
How to Find Your AC Filter Size - Step by Step
Finding your air conditioner filter size or central air filter size is easy:
- Check Your Current Filter: Look for the size printed on the filter frame (e.g., 16x25x1)
- Measure If No Size Is Visible: Use a tape measure to get length × width × depth
- Round to Nearest Inch: This gives you the nominal size to search for
- Verify Actual Dimensions: Check product descriptions for exact measurements
Frequently Asked Questions About Furnace Filter Sizes
What's the most common furnace filter size?
The 16x25x1 furnace filter is the most common size in American homes, followed closely by 20x20x1 and 16x20x1. These sizes fit most standard residential HVAC systems.
How often should I change my furnace filter?
For 1-inch filters: MERV 8 filters last 3 months, MERV 11 filters last 2-3 months, and MERV 13 filters should be changed every 1-2 months for optimal performance.
Can I use a different brand filter than my furnace manufacturer?
Yes! As long as the nominal size matches and the actual dimensions are close (within 1/4 inch), any brand will work. Our Atomic Filters fit all major HVAC brands.
What happens if my filter is too small or too big?
A filter that's too small allows unfiltered air to bypass the filter, reducing efficiency. A filter that's too large won't fit properly. Always verify both nominal and actual sizes before purchasing.
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Shop All Filter Sizes →Related Furnace Filter Guides
- Best 16x25x1 Air Filters for Allergies
- Finding the Best 16x20x1 Furnace Filter
- 20x25x1 Air Filter Buying Guide
- MERV 8 vs MERV 11: Which Is Right for You?
- How to Choose the Right Air Filter Every Time
Furnace Filter Air Flow Direction - Install It Right
Installing your filter correctly is crucial for system efficiency:
Air Flow Rule: The arrow on your filter should point TOWARD the furnace/air handler and AWAY from the return duct. Air flows from the room into the filter (front) and out toward the equipment (back).
What happens if installed backwards? A reversed filter restricts airflow, makes your system work harder, increases energy costs, and can damage your HVAC equipment over time.
Need Help Finding Your Filter Size?
Our filter experts are here to help! Contact us with your furnace model or filter measurements.
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