Better air starts with the right filter. And finding the right filter starts with understanding a few numbers.
At TRU Filtered Air, we’re on a mission to make breathing cleaner air ridiculously easy. Because when you consider how much time we spend indoors, taking care of the air in our homes should be just as natural as taking care of the water we drink.
That’s why we’ve made finding, ordering, and replacing your air filters as simple as possible.
Not sure what those numbers on your filter mean? We’ve put together a straightforward air filter size chart to help you find exactly what your home needs, without the guesswork.
How to Read an Air Filter Size Chart
Every size on an air filter size chart follows the same format: length x width x depth, in inches. A filter labeled 16x25x1 has a 16 by 25 inch face and is 1 inch thick.
- The first two numbers are the face of the filter, the side you see when you pull it out. Their order doesn’t matter, so 16x25x1 and 25x16x1 are the same filter.
- The last number is the depth, or thickness. It has to match the slot your filter slides into.
These are nominal sizes: rounded numbers made for ordering. If you measure the filter itself, you’ll usually get something a little smaller, like about 19.5 x 24.5 x 0.75 inches for a 20x25x1. That’s normal, and it’s how the filter slides into the rails without getting stuck. Our guide on how to measure air filter size walks through nominal vs. actual size in detail. You’ll see the same length x width x depth format in most sizing guides, including this overview of common air filter sizes.
Air Filter Size Chart: Every Size Tru Filtered Air Offers
Here are all 48 sizes available on our Shop Filters page, grouped by the first number on the frame. Every one is 1 inch thick, the standard depth for most home return vents and filter slots.
| If your size starts with | Sizes we offer |
|---|---|
| 10 inches | 10x20x1, 10x24x1, 10x30x1 |
| 12 inches | 12x12x1, 12x18x1, 12x20x1, 12x24x1, 12x30x1, 12x36x1 |
| 14 inches | 14x14x1, 14x18x1, 14x20x1, 14x24x1, 14x25x1, 14x30x1 |
| 15 inches | 15x20x1, 15x30x1 |
| 16 inches | 16x16x1, 16x20x1, 16.5×21.5×1, 16x24x1, 16x25x1, 16x30x1 |
| 17 inches | 17.5×17.5×1, 17x20x1, 17.5×23.5×1, 17x29x1 |
| 18 inches | 18x18x1, 18x20x1, 18x24x1, 18x25x1, 18x30x1, 18x36x1 |
| 20 inches | 20x20x1, 20x22x1, 20x24x1, 20x25x1, 20x30x1, 20x36x1 |
| 21 inches | 21x22x1, 21.5×23.5×1 |
| 22 inches | 22x22x1 |
| 23 inches | 23.5×23.5×1 |
| 24 inches | 24x24x1, 24x30x1, 24x36x1 |
| 25 inches | 25x25x1, 25x30x1 |
A few sizes on the chart include half inches, like 16.5×21.5×1 and 23.5×23.5×1. If your frame lists one of these, order it exactly as printed instead of rounding to the nearest whole number.
How to Find Your Size on the Chart
- Read the frame of your current filter. The size is usually printed along the long edge, sometimes on two sides. Some furnaces also list the recommended size on a sticker inside the door.
- Find the first number in the left column, then look for your full size in that row. The first two numbers can be in either order, so check both.
- Check the depth. Every size on this chart is 1 inch thick. If your filter or slot is noticeably thicker, see the FAQ below before you order.
If the label is worn off or there’s no filter in the slot, measure the opening and round to the nearest inch. Our step-by-step guide on measuring air filter size covers exactly how to do it, including what to do when your opening isn’t a standard size.
Air Filter Size Chart Mistakes to Avoid
- Ordering the size you measured. If your tape measure says 19.5 x 24.5, the filter you want is 20x25x1. Order the nominal size printed on the frame.
- Rounding a half-inch size. If the frame says 17.5×23.5×1, an 18x24x1 won’t fit the same way. Order exactly what’s printed.
- Ignoring the depth. A filter that’s too thick won’t slide in, and one that’s too thin for the slot can sit loose and let air slip around the edges instead of through the filter.
- Assuming every vent takes the same size. Homes with more than one return vent often use a different size in each. Note every size before you order.
- Forgetting the arrow. Once you have the right size, the arrow on the frame shows which way it goes in. Here’s our quick guide to furnace filter direction.
Why the Right Size Matters for Your Air
A filter can only clean the air that actually passes through it. When the size is right, the frame sits snug in the slot and air moves through the filter media instead of around it. When the size is off, even by a little, some of that air skips the filter entirely.
That’s also why fit and airflow go hand in hand in how we design our filters. Every Tru Filtered Air filter is a carbon-backed MERV 11 (Minimum Efficiency Reporting Value) filter, with optimally spaced pleats and high-loft media that reach up to 90% efficiency while letting your system breathe. The bonded activated carbon layer also captures odors, gases and VOCs (volatile organic compounds) that particle-only filters let through. Take a look at how our carbon-backed MERV 11 filters are built, or learn more about MERV ratings for air conditioner and heating filters.
Air Wellness: Find Your Size Once
If buying filters has ever felt harder than it should, it’s not you. Standing in a hardware store aisle trying to remember a size, then forgetting the extras in a cabinet, is a system built for guesswork.
Air Wellness works the other way around. The air in your home is part of your health, so caring for it should be one easy decision, not a recurring chore. Find your size on the chart once, pick it on our Shop Filters page, and choose delivery every month, every two months or every three months. From there, premium carbon-backed MERV 11 air filters arrive at your door exactly when it’s time to replace them. Nothing to remember, nothing to forget.
FAQ: Air Filter Size Chart Questions
Q: What are the most common air filter sizes?
A: Sizes like 16x20x1, 16x25x1, 20x20x1 and 20x25x1 show up in a lot of homes, but there’s no universal size. The number printed on your current filter’s frame is always the best answer.
Q: Is a 16x25x1 the same as a 25x16x1?
A: Yes. The first two numbers describe the face of the filter, and their order doesn’t change the fit. Just make sure the depth matches too.
Q: Why does my filter measure smaller than the size on the chart?
A: Charts list nominal sizes, which are rounded for ordering. A filter’s actual size is usually a bit smaller so it slides into the slot easily. Order the nominal size.
Q: What if my size isn’t on the chart?
A: Double-check the frame or measure the opening (our guide on how to measure air filter size can help). If your size still isn’t listed, or your system uses a thicker filter, reach out to our team at TruSupport@TruFilteredAir.com or 888-TRU-2298 and we’ll help you find the right fit.
Q: How often should I replace my air filter?
A: A common guideline is every three months, and sooner for homes with pets, allergies, heavy dust or smoke season. With a Tru Filtered Air subscription, your filter arrives on the schedule you choose, so the replacement is already at your door when it’s time.
Conclusion: Read the Frame, Find It on the Chart, Order Once
An air filter size chart turns three numbers into a quick decision. Read the nominal size on your filter frame, find it on the chart, make sure the depth matches, and you’re done.
At Tru Filtered Air, we make that the last time you have to think about it. Choose your size and delivery schedule on our Shop Filters page, and let clean air show up on repeat.
