# Reply To: Please help me do the math…

Forums › Air Tanks, Pumps, Compressors, & Filters › Please help me do the math… › Reply To: Please help me do the math…

“ztirffritz”Why not use the Crosman fill calculator?

http://www.crosman.com/discover/airguns/pcp-resources/fill-calculator

Pick your gun (Marauder), pick Scuba tank and enter the actual volume tank size and tank fill pressure, and your gun pressure range.

I will mention, that most SCBA tanks are listed in either minutes or Cubic Feet of compressed air that they’ll hold. For example, I have a Draeger 66cft/45min tank, but all the fill calculators ask for the water volume of the tank (ie the actual physical volume of the tank). I haven’t been able to find that anywhere. I could probably estimate it by getting the diameter and height of the tank and fudging a bit, but I’ve not yet found any place that lists the volume of my tank in cubic inches.

I’m guessing, even after the detailed explanation you haven’t read his post. He wanted the “Math” behind the calculator.

Anyway your Draeger 45min tank (it’s actually 46 min according to Draeger) would be 6.8L water volume (or fluid capacity as I had mentioned above). You can get that information from page 5 of the below linked PDF.

"ztirffritz"Why not use the Crosman fill calculator? http://www.crosman.com/discover/airguns/pcp-resources/fill-calculator Pick your gun (Marauder), pick Scuba tank and enter the actual volume tank size and tank fill pressure, and your gun pressure range. I will mention, that most SCBA tanks are listed in either minutes or Cubic Feet of compressed air that they'll hold. For example, I have a Draeger 66cft/45min tank, but all the fill calculators ask for the water volume of the tank (ie the actual physical volume of the tank). I haven't been able to find that anywhere. I could probably estimate it by getting the diameter and height of the tank and fudging a bit, but I've not yet found any place that lists the volume of my tank in cubic inches.I'm guessing, even after the detailed explanation you haven't read his post. He wanted the "Math" behind the calculator. Anyway your Draeger 45min tank (it's actually 46 min according to Draeger) would be 6.8L water volume (or fluid capacity as I had mentioned above). You can get that information from page 5 of the below linked PDF. http://www.draeger.com/sites/assets/PublishingImages/Products/cre_cylinders/global-blueprint/compressed-air-breathing-cylinders-pi-9046796-en-gb.pdf