How many CFM per ton is standard for residential HVAC?

The standard nominal airflow for residential air conditioning is 400 CFM per ton of cooling capacity. In humid climates (like the Gulf Coast), technicians often drop airflow to 350 CFM/ton for increased dehumidification, while dry desert climates run at 450 CFM/ton.

What happens if HVAC airflow is too low?

Low airflow (under 300 CFM/ton) causes evaporator coil freezing, liquid refrigerant floodback to the compressor, high static pressure, and premature blower motor burnout.

FREE HVAC TOOL ACCA MANUAL D AIRFLOW

HVAC CFM Airflow & Duct
Calculator

Calculate target system CFM airflow, climate-adjusted CFM/ton ratios, and recommended main trunk supply/return duct sizes in seconds.

Equipment & Climate Specs

Cooling System Capacity (Tons)

Climate & Dehumidification Target

Design Friction Rate (In. W.C. per 100 Ft)

Total System Airflow (CFM)
1,200 CFM
400 CFM per Ton across 3.0 Tons

Recommended Main Supply Trunk

16" Round (or 20"×10" Rect)

Velocity target < 900 FPM for quiet operation

Recommended Main Return Trunk

18" Round (or 24"×10" Rect)

Velocity target < 700 FPM to prevent filter whistle

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HVAC CFM Airflow & DuctCalculator

Equipment & Climate Specs

HVAC CFM Airflow & Duct
Calculator