Formula
CFM = tons × CFM/ton or CFM = Q_sensible ÷ (1.08 × ΔT)Standard: 400 CFM/ton (350 dry climate, 450 humid). Formula uses 1.08 = 0.24 (specific heat) × 60 min × 0.075 lb/ft³ (sea-level air).
Required airflow
1,200CFM
3 tons × 400 CFM/ton
Airflow within typical residential window (350–450 CFM/ton).