How to Determine Gallons in a Pond

It is essential to know the volume of your pond when preparing and administering water dechlorinators, algaecides or pond treatments. Safe and effective dosage depends on an accurate calculation of your pond's volume. If you have a regular-shaped pond, all you need is a simple mathematical formula. Alternatively, input your pond measurements into an online pond calculator, and it will do the hard work for you. You can easily calculate an irregular-shaped pond's volume using a bucket, hosepipe, stopwatch and a little math know-how.

Things You'll Need

  • Online pond calculator
  • Tape measure
  • 10-gallon bucket
  • Stopwatch
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Instructions

  1. Rectangular or Square Pond

    • 1

      Measure the dimensions of your pond, and write down the length, width and depth in feet.

    • 2

      Multiply length, by width, by depth, to determine the volume of your pond in cubic feet.

    • 3

      Multiply the total by 7.5 to find the volume of your pond in gallons.

    Circular Pond

    • 4

      Measure the diameter of your circular pond at the water's surface and the bottom of the pond. If your pond has vertical sides and is the same depth from top to bottom, the reading will be the same for both measurements.

    • 5

      Locate the center of your pond and measure the depth at this point. Multiply the surface diameter by the bottom diameter. Multiply the total by the central depth measurement.

    • 6

      Multiply the final figure by 0.785 to determine the volume of your pond in gallons.

    Irregular Pond Shape

    • 7

      Turn on a water hose to full strength. Using a stopwatch, monitor and record the length of time required to fill a 10-gallon bucket with water. Do not turn off the water valve after filling the bucket because the water flow rate must be exactly the same when you fill the pond.

    • 8

      Hold the running hosepipe in one hand and the stopwatch in the other. Drop the hose into your empty pond, and restart the stopwatch at the same time. Write down the length of time needed for the pond to reach capacity.

    • 9

      Divide the time required to fill the pond by the time required to fill the 10-gallon bucket. Multiply this answer by 10 for the volume of your pond in gallons.