How do I measure my air filter, or furnace filter ?
Most air filters have their dimensions stated in their nominal state which simply means the actual dimensions of the filter is rounded up or down. Below is an example of the nominal dimensions, and the actual size of the air filter compared to each other.
| |
Filter A |
Filter B |
|---|
| Nominal Dimensions |
16 x 25 x 1" |
16 x 25 x 1" |
| Actual Dimensions |
15½ x 24½ x ¾" |
15¾ x 24¾ x 7/8" |
HOW TO DETERMINE THE SIZE AIR FILTER TO ORDER:
Method 1: If you are currently using
a throw-away fiberglass air filter, take the
size written on your existing air filter and deduct 1/4 inch from both sides.
For
example, if your throw away filter is: 20 X 20, then you would order
19 3/4 X 19 3/4 actual dimension.
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Method 2: Actually measure your existing
air filter, but be sure that your existing
filter fits well.
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Method 3: Measure the opening provided
for the air filter in your furnace, ceiling
filter grill, or wall filter grill and deduct 1/4 inch from both sides.
For example, if
the opening provided for the filter in your furnace measures 18 X 20, then
you
would order 17 3/4 X 19 3/4
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