Air Filter Sizes Chart 2025 | Find Your Exact Size
Find Your Perfect Filter Size in Seconds
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🔍 Quick Filter Finder Tool
Enter your current filter size, model number, or measurements:
💡 Tip: Find the size/model on your current filter's frame or in your HVAC manual
Whether you need a 20x20x1 air filter, 16x25x1 furnace filter, or any of our 400+ sizes, we have your exact furnace filter dimensions in stock and ready to ship today. All filters are Made in USA with free shipping on qualifying orders.
How to Measure Your Air Filter - AC Filter Size Chart
Understanding HVAC filter measurements - Air filters have two sizes you need to know:
- Nominal Size: The rounded size printed on the filter label (like 20x20x1)
- Actual Size: The exact measurements (like 19.5x19.5x0.75)
🔍 Quick Tip: Finding Your AC Filter Size
Check the side of your current filter for the printed size, or measure Length x Width x Depth and round up to the nearest inch. (*note: some manufacturers round down)
Most Popular Furnace Filter Sizes (October 2025)
Based on thousands of orders, these are our top-selling HVAC filter sizes:
Complete Air Filter Sizes Chart - All Furnace Filter Dimensions Available
Click any size below to shop filters with that dimension. All sizes available in MERV 8, MERV 11, and MERV 13 ratings. Learn more about choosing the right MERV rating for your needs.
Standard 1-Inch Filter Sizes
Thicker Filter Options
Need a thicker filter? We carry these depths:
- 2-Inch Air Filters - Extended life, better filtration
- 4-Inch Air Filters - Maximum filtration, longest lasting
- 5-Inch Air Filters - Premium whole-house filtration
Understanding Nominal vs Actual Filter Dimensions - HVAC Filter Measurements
The size printed on your filter (nominal) is typically rounded up from the actual measurements. Here are common examples of furnace filter dimensions:
| Nominal Size (Label Size) |
Actual Size (True Dimensions) |
Shop This Size |
|---|---|---|
| 20x20x1 | 19.5 x 19.5 x 0.75 | Shop 20x20x1 → |
| 16x25x1 | 15.5 x 24.5 x 0.75 | Shop 16x25x1 → |
| 20x25x1 | 19.5 x 24.5 x 0.75 | Shop 20x25x1 → |
| 16x20x1 | 15.5 x 19.5 x 0.75 | Shop 16x20x1 → |
| 20x30x1 | 19.75 x 29.75 x 0.75 | Shop 20x30x1 → |
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 → |
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 → |
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.
Why Atomic Filters vs FilterKing & FilterBuy?
Can't Find Your Size?
We carry over 400+ sizes including custom dimensions. If your size isn't listed:
- 📞 Call us at 1-910-401-3910
- 💬 Use our live chat (bottom right)
- 📧 Email: info@atomicfilters.com
We'll find your exact size or create a custom filter!
Frequently Asked Questions About Air Filter Sizes
What's the difference between nominal and actual filter size?
Nominal size is the rounded size printed on the filter label (like 20x20x1), while actual size is the exact measurement (like 19.5x19.5x0.75). Always order by the nominal size unless specifically instructed otherwise.
What if my filter size is too big?
An oversized filter won't fit properly and may damage when forcing it in. This creates gaps that allow unfiltered air to bypass the filter, reducing your indoor air quality. Always choose the correct size or go one size smaller if needed.
What if my filter is too small?
Undersized filters leave gaps around the edges, allowing dust and allergens into your HVAC system. They also clog faster due to reduced surface area, making your system work harder and increasing energy costs.
How do I find my filter size without an old filter?
Check these locations:
- Look for a size printed on the filter slot or door
- Measure the filter opening and round up to the nearest inch
- Check your HVAC system manual or model number online
- Contact us with your HVAC model - we'll help you find the right size
Can I use a different brand filter if the nominal size matches?
Yes, in most cases. However, actual dimensions can vary slightly between manufacturers. Our Atomic Filters are designed to match industry-standard actual sizes for each nominal size, ensuring compatibility with your system.
How often should I change my furnace filter?
For standard 1-inch filters, change every 30-90 days depending on usage, pets, and allergies. Thicker filters (2-inch or 4-inch) can last 3-6 months. Check monthly and replace when visibly dirty or when airflow seems restricted.
Video: How to Find the Right Replacement Filter
Watch this quick guide to learn how to find your filter size and avoid common mistakes:
Why Choose Atomic Filters?
Need Help Finding Your Filter Size?
Our filter experts are here to help! Contact us with your furnace model or filter measurements.
Contact Filter Experts →Ready to Find Your Perfect Filter?
Browse our complete selection of air filters in all sizes and MERV ratings
Shop All Filter SizesQuestions? Call us at 1-910-401-3910 or email info@atomicfilters.com
Helpful Resources
- MERV 8 vs MERV 11: Which Filter Is Right for You?
- How to Choose the Right Air Filter Every Time
- Complete List of Filter Sizes with MERV Ratings
- Replacement Air Purifier Filters
🫁 When MERV 13 Makes a Real Difference
While MERV 11 works well for most homes, MERV 13 provides hospital-grade filtration that can be life-changing for specific situations:
Consider MERV 13 if:
- Severe asthma: MERV 13 captures 85% of 1-3 micron particles vs 65% for MERV 11 - this 20% difference can mean fewer asthma attacks
- Immunocompromised family members: Cancer patients, transplant recipients, or those with autoimmune conditions benefit from the highest filtration possible
- Newborns or infants: Developing lungs are more vulnerable to airborne particles
- COPD or chronic respiratory illness: Every bit of particle reduction matters
- High pollution areas: Living near highways, industrial zones, or wildfire-prone regions
📊 The Health Math:
Annual cost difference: $40-72 more for MERV 13
What you get: 20% better capture of fine particles that trigger respiratory issues
Real-world perspective: If your family experiences even 2-3 fewer doctor visits or 1 avoided ER visit per year due to better air quality, the MERV 13 upgrade pays for itself.
Most Families Don't Need MERV 13
If you have mild seasonal allergies and generally healthy family members, MERV 11 provides excellent protection at a lower cost. Save the MERV 13 upgrade for situations where respiratory health is a serious concern.
Medical Disclaimer: Air filters are not medical devices and are not intended to treat, cure, or prevent any disease. For persistent respiratory symptoms or health concerns, consult with licensed healthcare providers.