Come on Spinner... Think... You can figure it out with the info provided by CCrew...<br /><br />Here's an example... A tank that measures 25"long X 18" deep X 12" wide...<br /><br />break it down.. <br />18" X 12" = 216"...<br />216" X 25" = 5400"...<br />5400 divided by 231 = 23.376623 gallons..