If you know the approximate diameter, you can estimate the volume of a tank in gallons per inch.  Polyethylene by its nature will change depending upon temperature. Tank's dimensions will vary from batch to batch.

Poly tank size designations are nominal. All calculations on this page are approximate.

D = Inside diameter (inches)
C = Height of cone (inches)
S = Height of sloped floor (inches)
W = Height of vertical walls (inches)

For example, 500 gallon tank, flat floor:

D = 44"
C = 6"
W = 71"

Approximate volumes:

Volume per inch = 44 ² X .0034 = 6.6 gallons per inch
Volume of cone = 44 ² X .0034 X 6 / 3 = 13.2 gallons
Total volume = 6.6 X 71 = 468.6 + 13.2 = 481.8 gallons

If the 500 gallon tank were a sloped bottom, you would need to calculate the total volume as if it were a flat bottom tank, and then deduct for the sloped portion:

S = 44 X .75 / 12 = 2.75"
Volume of sloped portion = 44 ² X .0034 X 2.75 / 2 = 9.1 gallons
Total volume of a sloped floor tank = 481.8 - 9.1 = 472.7 gallons

If you have questions or need clarification, please don't hesitate to email us at sales@pascopoly.com or for detailed information including a quote, use our quote form.  Feel welcome to call us at (208) 549-1861 as well.