Duct Fitting Pressure Loss Calculator

Inputs

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Velocity at the fitting (flow ÷ duct area). The duct size calculator reports it from CFM and dimensions.
ft/min
From the ASHRAE Duct Fitting Database or SMACNA tables for your exact geometry. Orientation only: smooth-radius 90° elbows commonly tabulate near 0.2, mitered 90° elbows without vanes near 1.2, with single-thickness turning vanes roughly 0.2-0.35.
How many of this fitting at this velocity — the total is what the static-pressure budget feels.
Room-temperature sea-level air is about 1.2 kg/m³ (0.075 lb/ft³); thinner air at altitude lowers every dynamic loss.
lb/ft³

Results

Default result
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Loss per fitting(Δp)
0.168in. w.g.

C × VP — what this one fitting costs the static budget.

Also computed

Velocity pressure(VP)Pass0.14in. w.g.

ρV²/2 — the currency every dynamic loss is priced in.

Total for n fittings(ΣΔp)0.168in. w.g.

Method notes 4 notes
  • C comes from the published table for the exact geometry (ASHRAE Duct Fitting Database, SMACNA) — entry/exit conditions, aspect ratio and Reynolds range all move it. No coefficient tables are embedded here.
  • Dynamic losses scale with velocity squared: halving the velocity cuts every fitting loss to a quarter — usually cheaper than fighting for static.
  • Straight-run friction is a separate term — the duct friction loss calculator covers it; this screen prices the fittings between the straight runs.
  • Sum fitting and friction losses into the total external static budget and compare against the blower table (the HVAC static pressure calculator does the bookkeeping).

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