A Guess Isn’t Worth It
Guesses and wrong calculations are often more than 100 gallons off! A hundred gallons can mean the difference between a healthy dose or an overdose of medication and, in turn, the difference between life and death of pond inhabitants. In our pond department at Zamzows, we use the following three formulas to calculate the gallon quantity of a pond:
The Formula for an Exact Square or Rectangle Pond
Length x Width x Depth x 7.5
An example is as follows: pond length is 26 feet; the pond width is 8 feet, while the average depth is 4 feet. As indicated in the instructions above, follow this equation: 26’ X 8’ X 4’ X 7.5 = 6,240 gallons.
If the pond is an exact circle and no plant shelves we can get an exact measurement.
3.14 x Radius x Radius x Depth x 7.5
To do this, measure across the middle of the circle. This is the Diameter of the pond. 1/2 of the Diameter is called the Radius. A circular pond that is 10 feet wide (10 ft. Diameter) and is 3 feet deep has a Radius of 5 feet (1/2 the Diameter) so the formula would be 3.14 x 5 (R) x 5 (R) x 3 (D) x 7.5 and that would equal exactly 1766.25 gallons.
For irregular Shaped Ponds
Avg. Length x Avg. Width x Avg. Depth x 7.0**
We must use common sense when measuring a pond that is not a circle or square. Most ponds fit that description. The trick is to find an average for the measurements then use the formula. We chose 7.0 as a measurement for gallons per cubic foot because it will allow for rounded corners. For example A kidney bean shaped pond measures 10 feet in Length. In Width, it measures 5 feet but there’s a small section in the middle where it’s only 4 feet wide. So we’ll consider the Width measurement to be 4.75. It has no plant shelves or tiers and is uniformly 3 feet in Depth. This calculates to 997.5, roughly 1000 gallons.
Let’s take that a step further and say that the edge of the pond is completely surrounded by a shelf that is 1 foot in Depth but the rest of the pond is 3 feet. We might average that to be 2.5 feet. This changes our calculations to 10 (L) x 4.75 (W) x 2.5 (D) x 7.0. The gallons are now roughly 830.
More Accurate Measurements for Irregular Shaped Ponds
The Most Accurate Way
Sometimes we might want to try to get the most accurate calculation as possible, such as in the case of performing a potassium permanganate treatment which requires careful dosing. If a pond can be divided into squares, triangles, ovals or circles we can literally divide them and calculate more accurately the number of gallons a pond holds. For example, a pond that is a “figure 8” can easily be divided into 2 separate circles. Calculate each circle with the formula and it will result in a better calculation than by averaging the measurements.
Now that you know the exact gallons of your pond, you can accurately measure the correct dosage of algaecides, antibacterial products or parasitic treatment. By knowing the exact gallons, you will be treating your pond in a confident manner, and not placing your pond life in jeopardy. This important piece of information is paramount when purchasing pumps, filters, and pond tubing. You could be wasting your money by purchasing something too big, or a pump that under performs to your standards.
If you have questions, or simply would like for us to help you calculate the approximate gallons, stop by any Zamzows store with your pond measurement.