Well Volume Calculator

A water well is modeled mathematically as a vertical cylinder. The core equation relies on finding the cross-sectional area of the circular bore and multiplying it by the height of the water column. The fundamental formula for a single well volume is V = π * (d / 2)^2 * h, where d is the casing diameter and h is the height of the water column (Height 2 minus Height 1). To determine the three-well volume needed for heavy sanitization or shock chlorination, the tool simply multiplies this baseline single volume by three.

Imagine you have a residential water well with a casing diameter of 6 inches (0.5 feet) and a standing water column height of 100 feet. First, find the radius by dividing the diameter by two, yielding 0.25 feet. Next, square that radius to get 0.0625. Multiply that result by pi (~3.14159) to find the cross-sectional area of approximately 0.0491 square feet. Multiply this area by the 100-foot height to find a single well volume of roughly 4.91 cubic feet. Converting cubic feet to gallons (by multiplying by 7.48052), your single well volume is approximately 36.7 gallons. For maintenance procedures requiring three well volumes, you would multiply 36.7 by 3, totaling about 110.1 gallons of water.

Always measure your casing diameter accurately from the interior walls rather than the exterior surface to avoid calculation errors. When determining water column height, use a reliable well sounder or weighted tape measure to find the exact distance from the water surface to the bottom of the well. Keep in mind that well casing diameters are frequently measured in inches while depths are measured in feet, so proper unit conversion is critical for accurate results.