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Where to find your air filter size
Most disposable HVAC filters have their size printed along the outer frame. Look for three numbers separated by an “x,” such as 16 × 20 × 1 or 20 × 25 × 1. You may also see a second, slightly smaller set of measurements labeled “actual size.”
Check every edge of the frame before measuring. The size may be printed in small text near the airflow arrow, MERV rating, manufacturer name, or model number.
Know the difference
Nominal size vs. actual size
The nominal size is the rounded name used to shop for the filter. The actual size is the filter’s physical measurement and is normally a little smaller so it can slide into the HVAC slot.
For example, a filter sold as 20 × 20 × 1 may physically measure approximately 19.5 × 19.5 × 0.75 inches. Exact dimensions can vary by manufacturer, so use the actual-size information shown on the FilterHome product page before ordering.
Measure correctly
How to measure an HVAC air filter
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1
Turn the HVAC system off
Switch the system off before opening the return grille or removing the existing filter.
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2
Remove the current filter
Measure the filter itself whenever one is available. This is usually more reliable than measuring the opening.
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3
Measure width, height, and depth
Measure from outside edge to outside edge and record all three dimensions to the nearest 1/8 inch.
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4
Match the measurements
Use the finder above to compare your actual measurements with FilterHome’s available nominal sizes.
Do not force a filter into the slot. A filter should fit securely without bending, crushing, or leaving a large gap around the frame.
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Common air filter sizes
Select a size below to view available MERV ratings, pack quantities, and subscription options.
Need an uncommon size?
We manufacture custom air filters
Enter the exact width, height, and depth you need. FilterHome manufactures standard and custom filters on Long Island, New York.Questions answered