What Size Pond Liner do I Need?

Using a liner in your pond is extremely essential as this is what stops water from leaking out through the base. With good quality item materials, water remains within the confines of the pond.

The liner also keeps debris out of the water to make it easier to maintain.

Nevertheless, you need to choose the perfect pond liner size to guarantee its effectiveness. After all, an incorrectly sized pond liner will not effectively hold water in and keep debris out.

To make it easier for you to find the perfect option, I’ve shared an in-depth guide on how to figure out the right size for your pond liner.

What Size Pond Liner do I Need Calculations

Determining the pond liner sizing you need has been made much easier. After all, ponds come in different shapes – most of them being irregular. Therefore, measuring every part of the pond would take hours. Instead, all you have to do is use the length and width of your pond to determine the size of the liner.

Irregular Pond liners

The length refers to the longest distance inside your pond whilst the width refers to the shortest distance inside your pond. After measuring the length and width, the next step is the calculations. Before, you start the calculation, prep the numbers. For the length, add the maximum length, twice the maximum depth of the pond liner, and at least an extra foot.

For the width, add the maximum width, twice the maximum depth, and at least an extra foot.  For both width and length, the additional foot is used to compensate for any error.  After all, if you remain with the extra liner, you can easily tuck it around the edges of the pond. In fact, if you have a larger pond, you may have to double on the extra foot.

Now, let’s put the calculation into practice.

If you have a pond that measures 12 feet long and 5 feet wide with a 2 feet depth, you will need a line that measures 17 feet long by 10 feet wider. This is how the calculations work:

But, this is only the basic calculation. To be able to measure any pond liner, you want to master the calculations. As mentioned above, the depth included in the calculation is the deepest value. However, if you have a pond with a sloped depth, simply average the minimum and maximum depth measurements to get the actual value. As a general rule of thumb, you can use the formula outlined below when shopping for any pond liner:

U-Shaped and L-Shaped Pond Liner Sizing

Measuring L-shaped and U-shaped ponds for liners may slightly vary.  To take accurate measurements for pond liner size, you have to divide the pond into sections.  For example, with an L-shaped pond, you will divide it into a square and rectangle.

This means that you will invest in a rectangle and square liners and then add a few measurements into each liner to cover the space where the two meet. Alternatively, you can calculate them in full shape. Generally, the formula for such complex shapes is as follows:

Why Overlap is Important

You will notice that all the formulas for calculating the pond liner size have an overlapping value. The overlap value is extremely important for the calculations. After all, fitting a pond liner is amongst the most cumbersome and frustrating tasks.

Adding an overlap gives you peace of mind. Typically, you will need about 1 to 2 feet extra. This ensures that the liner will get secured to the ground when fitted underneath the pond.  The overlap acts as insurance for any errors.  After all, it’s much easier to deal with an oversized liner than it is to deal with an undersized one.

With an oversized liner, you can simply fold it into the edges of the pond. An undersized one will simply be useless and ineffective. An undersized pond liner cannot be properly secured. Thus, it will end up sinking to the bottom and exposing the dirt sides when the pond is filled.

Additionally, having extra overlap protects the pond when you are adding water and other heavy elements. Placing the excess liner sides underneath heavy edging such as rocks holds it in place and ensures that the pond is adequately protected.