How to Calculate the Volume of Water in a Square Tank

By Bob White; Updated April 25, 2017
Determining how many gallons in a tank tells you what fish to put in it.

Calculating the volume of water in a square tank is a useful life skill. This can be used to determine the amount of conditioners and chemicals to add to a specific volume of water, or how much water you need to fill a pool or fish tank. To make this calculation, you first need to figure out the square footage of the tank, and then multiply that by the constant number of gallons per square feet.

Measure the width of the tank with a measuring tape. If your tank is a rectangle, also measure the height and depth.

Multiply its width by its height by its depth. The result is the cubic feet of space the tank holds.

Multiply the result by 7.48. The answer is the number of gallons of water the tank holds. 7.48 is a the number of gallons in a square foot of space.

About the Author

Bob White began his writing career in 2006. Working in sales, he was a technical writer tasked with responding to requests for proposal. White has a Bachelor of Arts in computer science and a diploma in home inspection. He has also worked in construction, landscaping and the pool industry for more than 15 years.