🪣 Well Volume Calculator
Estimate how many gallons of water are stored in your well based on the casing diameter and the height of the water column.
What this calculator does
The Well Volume Calculator estimates how many gallons of water are held inside a well’s casing, using just the casing’s inside diameter and the height of the standing water column (the static water level up to the bottom of the well, or the pumping level).
How the formula works
A well casing is essentially a cylinder, so its stored water volume follows the standard cylinder formula: Volume = π × radius² × height. The calculator converts the diameter from inches to feet, squares the radius, multiplies by the water column height, and then converts cubic feet to gallons using the standard conversion of 7.48052 gallons per cubic foot.
This is a geometric estimate based on the casing alone; it does not account for gravel pack, well screen design, or any water stored in the surrounding aquifer formation itself. For well planning, water system sizing, or general reference, treat this as an approximation rather than a precise measurement — an actual sounding of your well is the most accurate way to know your water column height.