Effortlessly determine the ideal HVAC duct size for your heating, ventilation, and air conditioning system. Our CFM calculator helps you achieve optimal airflow, energy efficiency, and comfort in any space. Get accurate results for residential or commercial projects.
Formula:
Formulas Used:
Our calculator uses the following fundamental HVAC formulas:
1. Required Cross-Sectional Area (A):
Asq.ft. = CFM / Velocity
Asq.in. = Asq.ft. × 144
2. Equivalent Round Duct Diameter (D):
Dinches = √( (4 × Asq.in.) / π )
3. Rectangular Duct Dimensions (W, H - for same Asq.in.):
- For a square duct (W = H):
W = H = √Asq.in. - For a 2:1 aspect ratio duct (W = 2H):
H = √(Asq.in. / 2)andW = 2 × H
Where:
- CFM = Cubic Feet per Minute (airflow rate)
- Velocity = Feet per Minute (air speed)
- Asq.ft. = Cross-sectional Area in Square Feet
- Asq.in. = Cross-sectional Area in Square Inches
- Dinches = Equivalent Round Duct Diameter in Inches
- W = Rectangular Duct Width in Inches
- H = Rectangular Duct Height in Inches
- π ≈ 3.14159 (Pi)