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HEPA Filter Bank Pressure Drop Estimator

Estimate a HEPA filter bank's current pressure drop between its rated clean and final (loaded) values, based on a loading percentage.

Computed in your browser — nothing you enter is uploaded. Figures are presented for United States against IRC 2024, and every formula is cited under regulatory standards below.

Last verified 2026-08-26 · v1.0.0

Market
Imperial · sales tax

Estimated current pressure drop

1.5 in. w.g.

Low confidence

Filter pressure drop is unique to each manufacturer's media and construction — always use the actual filter's data sheet for the rated clean and final pressure drop values, not an assumed default. This calculator only linearly interpolates between the two rated values you supply; real filter loading curves are not perfectly linear.

With the figures above, the estimated current pressure drop comes to 1.50 in. w.g.. Treat this one cautiously — the confidence rating is low, so verify it against a merchant quote or a trade opinion first. This is calculated for United States and cites IRC 2024. Building in another market? Change the selector above so the units and code reference follow.

Add the equipment this sizes

This result is a specification — 1.5 in. w.g. — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — confirmed fixes become pinned regression tests.

[Schema Verified] Computed in alignment with American Concrete Institute (ACI 318-19) formulas and International Residential Code (IRC 2024) spatial boundaries.

Regulatory standards & verification citations

  • Filter pressure drop is inherently manufacturer- and media-specific — there is no general industry formula analogous to a duct friction chart. This calculator interpolates between the filter manufacturer's rated clean (initial) pressure drop and its rated final (replacement) pressure drop, based on a user-estimated loading percentage: current ΔP = clean ΔP + (final ΔP − clean ΔP) × (loading % ÷ 100). Typical standard HEPA filters are commonly rated around 0.5-1.5 in. w.g. clean and roughly double that at final loading, but the specific filter's data sheet governs — these are not universal constants.

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Frequently asked questions

Why isn't there a standard formula for HEPA filter pressure drop, like there is for duct friction?
Filter pressure drop is inherently manufacturer- and media-specific — it depends on the pleat pack design, media type, and construction of that particular filter, so there is no general industry formula analogous to a duct friction chart. This calculator instead interpolates between the manufacturer's own rated clean and final pressure drop values.
Where do I find the clean and final pressure drop values for my filter?
Always use the actual filter's data sheet for these values rather than an assumed default. Typical standard HEPA filters are commonly rated around 0.5-1.5 in. w.g. clean and roughly double that at final loading, but the specific filter's published ratings govern.
Is the interpolation between clean and final pressure drop exact?
No — this calculator only linearly interpolates between the two rated values you supply based on your estimated loading percentage. Real filter loading curves are not perfectly linear, so treat the result as an estimate rather than a measured reading.