Fill An Air Tank

How long does it take for your air compressor to fill an air tank?

I have been asked that question many times on this website, and since there appears to be a good deal of interest, I have added a page to this site dealing with how long it takes to fill an air tank.

How long to fill an air tank? You need to
        gather this information

  • V = Tank size
  • Final pressure (cut-out pressure)
  • Initial pressure (cut-in pressure)
  • 7.48 - conversion from gallons to CFM
  • Atmospheric pressure = 14.7
  • Compressor Pump Delivery in CFM

Then, you apply the information to the following formula:

fill an air tank formula


  • My tank size = 100 gallons
  • Cut-out pressure = 160 PSI
  • Cut-in pressure = 80 PSI
  • Conversion = 7.48
  • Atmospheric pressure = 14.7
  • Compressor Pump capacity = 4 CFM

That gives us:

compressed air formula


100 x 80 = 8,000

Divided by:

440 (7.48 x 14.7 x 4 rounded up)

= 18.2 minutes

Folks, you are welcome to use these calculations yet be a bit cautious. While the information is sourced from a number of reputable locations I cannot be 100% sure of the accuracy, and therefore, you use this information at your own risk.

If you need to be 100% sure, get an engineer to help you.