If you have a pond on your property, you may need to figure out the pond's volume to properly treat the pond, provide enough oxygenation, or plan the number of fish you can add. With a few simple mathematical calculations, you can calculate pond volume fairly easily.
Determine what shape your pond is. There is a different calculation for each shape of pond.
Measure the pond's length, width and depth. To calculate depth, take a boat out on the pond. Take a weight and tie a string to it. You can then drop the weight down to the bottom of the pond and measure the distance from the weight to the water line on the string. Take many of these measurements all over the pond.
If the pond is small, like a backyard fish pond, it is even easier to measure depth! Use a tape measure to find the exact depth in multiple points of the pond. Extend the tape measure to the bottom of the pond and the depth will be where the water stops on the tape measure. Measure as many points as you can. Calculate the average depth by adding all the depth measurements and dividing by the number of measurements you took.
Calculate the pond's volume by using one of the following formulas. For oval ponds: length x width x depth x 6.7 = water volume in gallons. For circular ponds: length x width x depth x 5.9 = water volume in gallons. For rectangular ponds: length x width x depth x 7.5 = water volume in gallons.
For irregularly-shaped ponds, divide the pond into sections. Draw the pond on graph paper as close as you can to the actual shape. Then section the pond into different shapes on the graph paper, calculate the volume for each shape, and then add them all together to get a close estimate of the pond volume.
When measuring the depth of the pond, be sure to wear a life vest in case you fall in the water. You could possibly drown without one.