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Calculating your pond size / volume

When measuring your pond, bear in mind that your results will probably be an approximation: It’s unlikely that your pond will have vertical sides, the bottom won’t be flat and in most cases the width and length measurements will be an average. However, it’s still important to use it as a guide especially when looking for a pond pump, filter or using treatments.

To find the average length measure across the length of the pond at three points, add the values together and divide by three. Repeat the same process to find the average width and depth.

Once you have your measurements you can use our volume calculator to calculate your pond’s volume.

When using the calculator, you’ll need to know the following measurements of your pond (in cm):

  • Average Length 
  • Average Width
  • Average Depth

We’ll also need to know your pond’s shape – whether it’s rectangle/square, irregular/oval, or circle.

If you wish to calculate your pond volume manually, you can use the following formulas:

  • For a rectangle or square pond: Volume = Length x Width x Depth
  • For an irregular or oval-shaped pond: Volume = 0.8 x Length x Width x Depth
  • For a circular pond: Volume = 3.14 x Radius squared x Depth

For certain types of ponds like our preformed ponds, the volume and other measurements are provided.

Should I measure in litres or gallons?

Remember to convert the volume into litres for future reference, as most pond filter choices are based on litres, not gallons.

A UK gallon is 4.54 litres, so to convert the volume from gallons into litres, you need to use the following formula:

Volume (in gallons) x 4.546 = Volume in litres

So if your pond is 200 gallons in volume: 200 × 4.546 = 909.2 litres.

Why does the volume of my pond matter?

It cannot be understated the effect of your pond’s size and volume. Without understanding the size and volume of your pond, it can be difficult to ensure you have all the correct equipment and resources to maintain a healthy pond.

Ultimately, it can impact your pond in ways such as:

  • The amount of fish and plants your pond can support (see – how many fish?)
  • The amount of filtration needed, and whether additional filters are required
  • The size and power of your pond pump
  • The amount of treatments or additives you should use

Make sure you take the time to calculate these measurements, as this will help you determine the needs of your pond.

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