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CFM Airflow Calculator

Required CFM from BTU load and temperature split.

Inputs

Inputs and assumptions

Sensible load.

Supply-return split, 15-25 F typical. The 1.08 constant assumes sea-level air; above 2,000 ft add about 3% CFM per 1,000 ft of elevation.

Result

Required airflow (CFM)
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What to check

  • Sensible BTU load
  • Measured supply-return split

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Screening estimate only. Verify duct measurements, nameplate ratings, and installer quotes before making a decision.

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