Actual Size Versus Nominal Size
When measuring air filters, it is essential to understand the difference between the nominal size and the actual size. This is crucial for selecting the appropriate filter specifications for HVAC (Heating, Ventilation, and Air Conditioning) equipment, ensuring the effective capture of airborne contaminants, and maintaining the stable operation of the system. We have already compiled a list of standard sizes that cover both the nominal size and the actual size.
Actual Size:
The actual size of an air filter refers to its precise dimensions, often expressed in fractions, and typically measures 1/2” to 3/4” smaller than its nominal size. This slight reduction is known as the filter's "undercut."
Nominal Size:
The nominal size is the size obtained by rounding the actual size to the nearest whole number or half number. This is usually the size you will use when looking for a replacement filter.
|
Nominal Size |
Actual Size |
| 1" Stock Pleated Filter Sizes | |
|
10 X 10 X 1 |
9-1/3 X 9-1/3 X 3/4 |
|
10 X 20 X 1 |
9-1/3 X 19-1/3 X 3/4 |
|
10 X 24 X 1 |
9-1/3 X 23-1/3 X 3/4 |
|
10 X 30 X 1 |
9-1/3 X 29-1/3 X 3/4 |
|
10 X 36 X 1 |
9-1/3 X 35-1/3 X 3/4 |
|
12 X 12 X 1 |
11-1/3 X 11-1/3 X 3/4 |
|
12 X 16 X 1 |
11-1/3 X 15-1/3 X 3/4 |
|
12 X 20 X 1 |
11-1/3 X 19-1/3 X 3/4 |
|
12 X 24 X 1 |
11-1/3 X 23-1/3 X 3/4 |
|
12 X 30 X 1 |
11-1/3 X 29-1/3 X 3/4 |
|
12 X 36 X 1 |
11-1/3 X 35-1/3 X 3/4 |
|
14 X 14 X 1 |
13-1/3 X 13-1/3 X 3/4 |
|
14 X 18 X 1 |
13-1/3 X 17-1/3 X 3/4 |
|
14 X 20 X 1 |
13-1/3 X 19-1/3 X 3/4 |
|
14 X 24 X 1 |
13-1/3 X 23-1/3 X 3/4 |
|
14 X 25 X 1 |
13-1/3 X 24-1/3 X 3/4 |
|
14 X 30 X 1 |
13-1/3 X 29-1/3 X 3/4 |
|
15 X 20 X 1 |
14-1/3 X 19-1/3 X 3/4 |
|
16 X 16 X 1 |
15-1/3 X 15-1/3 X 3/4 |
|
16 X 20 X 1 |
15-1/3 X 19-1/3 X 3/4 |
|
16 X 24 X 1 |
15-1/3 X 23-1/3 X 3/4 |
|
16 X 25 X 1 |
15-1/3 X 24-1/3 X 3/4 |
|
16 X 30 X 1 |
15-1/3 X 29-1/3 X 3/4 |
|
16 X 36 X 1 |
15-1/3 X 35-1/3 X 3/4 |
|
18 X 18 X 1 |
17-1/3 X 17-1/3 X 3/4 |
|
18 X 20 X 1 |
17-1/3 X 19-1/3 X 3/4 |
|
18 X 24 X 1 |
17-1/3 X 23-1/3 X 3/4 |
|
18 X 25 X 1 |
17-1/3 X 24-1/3 X 3/4 |
|
18 X 30 X 1 |
17-1/3 X 29-1/3 X 3/4 |
|
18 X 36 X 1 |
17-1/3 X 35-1/3 X 3/4 |
|
20 X 20 X 1 |
19-1/3 X 19-1/3 X 3/4 |
|
20 X 24 X 1 |
19-1/3 X 23-1/3 X 3/4 |
|
20 X 25 X 1 |
19-1/3 X 24-1/3 X 3/4 |
|
20 X 30 X 1 |
19-1/3 X 29-1/3 X 3/4 |
|
20 X 36 X 1 |
19-1/3 X 35-1/3 X 3/4 |
|
22 X 22 X 1 |
21-3/4 X 21-1/3 X 3/4 |
|
22 X 24 x 1 |
21-1/3 X 23-1/3 X 3/4 |
|
24 X 24 X 1 |
23-1/3 X 23-1/3 X 3/4 |
|
24 X 36 X 1 |
23-1/3 X 35-1/3 X 3/4 |
|
25 X 25 X 1 |
24-1/3 X 24-1/3 X 3/4 |
|
25 X 32 X 1 |
24-1/3 X 31-1/3 X 3/4 |
| 2" Stock Pleated Filter Sizes | |
|
12 X 12 X 2 |
11-1/3 X 11-1/3 X 1-3/4 |
|
12 X 20 X 2 |
11-1/3 X 19-1/3 X 1-3/4 |
|
12 X 24 X 2 |
11-1/3 X 23-1/3 X 1-3/4 |
|
14 X 20 X 2 |
13-1/3 X 19-1/3 X 1-3/4 |
|
14 X 25 X 2 |
13-1/3 X 24-1/3 X 1-3/4 |
|
15 X 20 X 2 |
14-1/3 X 19-1/3 X 1-3/4 |
|
16 X 16 X 2 |
15-1/3 X 15-1/3 X 1-3/4 |
|
16 X 20 X 2 |
15-1/3 X 19-1/3 X 1-3/4 |
|
16 X 24 X 2 |
15-1/3 X 23-1/3 X 1-3/4 |
|
16 X 25 X 2 |
15-1/3 X 24-1/3 X 1-3/4 |
|
18 X 18 X 2 |
17-1/3 X 17-1/3 X 1-3/4 |
|
18 X 24 X 2 |
17-1/3 X 23-1/3 X 1-3/4 |
|
20 X 20 X 2 |
19-1/3 X 19-1/3 X 1-3/4 |
|
20 X 24 X 2 |
19-1/3 X 23-1/3 X 1-3/4 |
|
20 X 25 X 2 |
19-1/3 X 24-1/3 X 1-3/4 |
|
20 X 30 X 2 |
19-1/3 X 29-1/3 X 1-3/4 |
|
24 X 24 X 2 |
23-1/3 X 23-1/3 X 1-3/4 |
|
25 X 25 X 2 |
24-1/3 X 24-1/3 X 1-3/4 |
| 4" Stock Pleated Filter Sizes | |
|
12 X 24 X 4 |
11-1/3 X 23-1/3 X 3-3/4 |
|
16 X 20 X 4 |
15-1/3 X 19-1/3 X 3-3/4 |
|
16 X 25 X 4 |
15-1/3 X 24-1/3 X 3-3/4 |
|
18 X 24 X 4 |
17-1/3 X 23-1/3 X 3-3/4 |
|
20 X 20 X 4 |
19-1/3 X 19-1/3 X 3-3/4 |
|
20 X 24 X 4 |
19-1/3 X 23-1/3 X 3-3/4 |
|
20 X 25 X 4 |
19-1/3 X 24-1/3 X 3-3/4 |
|
24 X 24 X 4 |
23-1/3 X 23-1/3 X 3-3/4 |
We are committed to providing a "one-stop shop" service for all your air filtration needs. As an excellent air filter manufacturer, we are able to customize various types of air filters. If you are unsure about the size, please send an email to our experts for assistance.
Custom size filters will take eight to ten weeks to manufacture.
CUSTOM FILTERS ARE NONRETURNABLE.