Hay guys I just figured this out (all the smart guys already know this) My brew pot is 13.5 inches round inside dimensions and 17.5 inches tall inside dimensions. the radius of my pot is 13.5 / .5 = 6.75 inches I want to know how many inches it takes to get 5 gallons in my pot the formula is.....Pie x radius x radius ...(3.14 x 6.75 x 6.75 = 143.06625... or just 143 for my pot) to find the gallons the formula is..... inches x 143 Divide by 231 = gallons sooo 8 inches tall x 143 Divided by 231 is 4.95 gallons or close enough to 5 gallons in my pot 9.75 inches tall x 143 Divided by 231 is 6 gallons of water. etc. now I can use my measuring stick to figure out how many gallons of water are in my boil pot. or just use the long plastic spoon I normally use for mashing with markings on it.