Sizing Reference

Nominal vs. Exact Filter Sizes

When you order a custom or special-size pleated filter, it's important to understand the difference between nominal (labeled) size and exact (actual) size. This diagram shows the industry convention we follow.

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HVAC pleated filters: nominal vs exact size diagram for 1-inch, 2-inch, and 4-inch depths
Industry convention: exact size = nominal size minus ½” on each face dimension and minus ¼” on depth. Exception: exact size = nominal − ⅝” on each face dimension if one or both nominal dimensions are 24” on 2” and 4” nominal depths.

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