How to work out the size of your dam

Dams come in all shapes and sizes – but how do you know what the actual size of your dam is?

There is a simple formula to calculate the size of your dam, whether you need to know for treating algae, aquatic weeds, water aeration or water treatments through the use of algaecides, herbicides and aeration systems.

Size of your dam

Its easy, measure the length and width of your dam

Length = either with a tape measure or using your step length (average step length is 78cm)

Then with your measurements, follow one of the following calculations:

  • Square/rectangle – Calculate the length and width; L x W = surface area
  • Circle – Calculate radius (1/2 of the dam length); Pi x R2 or 3.14 x R x R = surface area
  • Triangle – Calculate the base and height; (0.5 x B) X H = surface area
  • Odd-shaped – Measure your dam in sections using the calculations above or use a handy online tool like Map Developers.

To determine how many acres your dam is, divide your value for surface area by 4,046 (the number of square metres per acre)


Deeper water bodies benefit greatly from bottom aerators such as our Air Pro Lakebed Aerator. Shallower water bodies may be better suited with a surface aerator; so understanding your dam’s depth is important to make sure you get an aeration system that will provide maximum oxygenation.

How to measure the depth of your dam: Start by using a string marked every 25cm, a weight (like a brick), a notepad & pencil, and a boat or canoe. Then, head out to the dam and follow these directions:

  1. Tightly attach the weight to one end of the string.
  2. Place your boat or canoe into the dam with your materials and move towards the centre of the dam.
  3. Drop the weighted string into the dam and note where it hits the bottom. Repeat in at least four other locations in the dam, more if your dam is particularly large. You can add all of these values together and divide by the total number of samples to get your dam’s average depth.


Shape is important when measuring a dam. Square dams are easy but irregular shaped dams can seem a little daunting. Not to worry, we have made it easy! Just break your dam into smaller sections and add it all together at the end. Irregular dams may have an island, inlet, uneven shorelines, or other unique features. These dams will often require more lakebed diffusers to ensure adequate circulation of oxygen.

by Aquatic Technologies
If you have any questions regarding looking after your dam or pond and what products are the most suitable for your situation, please read through the helpful articles on our site or feel free to contact our friendly team who can help you maintain proper health in your water body year round.
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