Fan Static Pressure Calculator

Build a total external static pressure (TESP) estimate component by component, then compare it with the fan or unit rating.

Pressure drops

Pre-filled with typical values — replace them with your calculated duct losses and manufacturer data.

Supply duct (critical path: friction + fittings) (in. w.g.)

Return duct (critical path) (in. w.g.)

Cooling coil, wet (in. w.g.)

Heating coil / heat exchanger (in. w.g.)

Filters, mid-life (MERV 8–13) (in. w.g.)

Supply diffuser / grille (in. w.g.)

Return grille (in. w.g.)

VAV box / terminal (minimum inlet ΔP) (in. w.g.)

Dampers, sound attenuators, other (in. w.g.)

Design margin (%)

Unit rated external static (optional) (in. w.g.)

Results

Review the pressure drops, then select Calculate.

Method and assumptions

TESP = sum of external component pressure drops on the critical (highest-loss) supply and return paths; design TESP = TESP × (1 + margin).
Duct values should come from the Duct Sizer, Equivalent Length or Fitting Loss calculators for the critical path only — not every run added together.
Pre-filled component values are typical rounded figures for comparison; coils, filters and terminals must use manufacturer data at the actual airflow.
Whether coil and filter losses count as 'external' depends on the unit's rating basis — check the manufacturer's fan table. Results shown to 0.01 in. w.g.

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Important Disclaimer

This calculator is for preliminary design guidance only. Final duct sizing, construction, and installation must be performed by qualified professionals and comply with applicable codes and standards.