Spray Gun CFM and Air Compressor Sizing Calculator
Calculate the total CFM (cubic feet per minute) required for your spray gun setup and determine the minimum air compressor size needed to run it continuously and efficiently.
Formulas Used
1. Effective Gun CFM Demand:
Effective_Gun_CFM = Gun_CFM × Number_of_Guns × (Duty_Cycle / 100)
2. Total Air Demand:
Total_Demand_CFM = Effective_Gun_CFM + Other_Tools_CFM
3. Required Compressor CFM:
Required_CFM = Total_Demand_CFM × (1 + Safety_Factor / 100)
4. Estimated Horsepower:
CFM_at_90PSI = Required_CFM × (Operating_PSI / 90)
HP ≈ CFM_at_90PSI / 3.5
(Industry rule of thumb: ~3.5 CFM per HP at 90 PSI for single-stage compressors)
5. Tank Runtime (if tank size entered):
Tank_Volume_ft³ = Tank_Gallons / 7.48052
Usable_Air_ft³ = Tank_Volume_ft³ × (PSI / 14.696)
Runtime_min = Usable_Air_ft³ / Required_CFM
Assumptions & References
- Spray gun CFM ratings are taken at the manufacturer's specified operating pressure. Always verify with your gun's spec sheet.
- A duty cycle of 75% is typical for intermittent spray painting; continuous production lines may approach 100%.
- A 25–50% safety/headroom factor is recommended by OSHA and compressor manufacturers to prevent overheating and pressure drop during peak demand.
- The HP estimate uses the industry standard of approximately 3.5 CFM per HP at 90 PSI for single-stage piston compressors (Compressed Air Challenge, DOE).
- Tank runtime assumes the tank starts fully pressurized and the compressor does not run during the calculation period (worst-case scenario).
- 1 gallon = 0.13368 ft³ (7.48052 gallons per cubic foot); atmospheric pressure = 14.696 PSI.
- HVLP guns typically require 15–25 CFM at 25–30 PSI at the air cap; conventional guns 10–20 CFM at 40–60 PSI.
- References: Compressed Air Challenge Best Practices, OSHA 29 CFR 1910.169, DeVilbiss/Binks spray equipment specifications.