How to Calculate the Volume of a Well

Why is this important?

The volume of the well is used to determine the amount of plugging material needed.
The volume is also used to determine the needed amount of disinfectant.
Assuming the wrong volume of the well could lead to many future problems.

Obtaining Well Dimensions

Diameter of the well-measured distance across the inner lip of the well
Total well depth-measured distance from top to bottom of well
Water depth-measured distance of depth of water in the well. (Tie a weight to some string and drop it to the bottom of the well. Retrieve the string and measure the portion of the string that is wet.)

Hand Dug Well Example

You have large hand dug well that is 3 feet in diameter and is 45 feet deep. The depth of water in the well is 10 feet.

The formula calculates the volume of the well

V = ((n * D2)/4)* d
Where:
n = 3.1416
D = diameter of well (feet)
d= depth of well (feet)

The volume of the well is

V = ((3.1416* 3²)/4) *45
V = 318.53 ft³
1 yd cubed = 27 ft³
V = 11.79 yd³/li>

An abandoned well is 6 inches in diameter, 100 feet in depth, and the water level is 40 feet.

The volume of the well is

D = 6in/12in/ft = 0.5 ft
V = ((3.1416* 0.52)/4) *100
V = 19.62 ft3

Online Calculator – Use Total Well Volume in feet or yards

Alternate Method

Use Table 1 Plugging Material Calculation Sheet
And the diameter of the well

Alternate Method – Table 1

Well/Hole DiameterCementBentonite Chips
InchesLinear FeetLinear Feet
250.331.3
328.813.9
416.21.9
510.45
67.23.5
75.32.6
842
93.21.5
102.61.3
121.80.86
141.30.63
1610.48
180.80.38
200.60.31
240.40.21
36.02.0.97
400.16.078
440.13.065
48.11.054
Bags of cement needed (94 lbs per sack)
100 feet/7.2 feet = 13.8 sacks
Bags of Bentonite needed (50 lbs per sack)
100 feet/3.5 feet = 28.5 sacks