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Pond Liner Calculator & Guide

Pond Liner Calculator & Guide

Installing a fish pond liner is a crucial first step to creating the pond of your dreams. But what size pond liner do you need? While sizing a liner may seem a bit intimidating at first, it's actually easier than you'd think. In this guide, we'll cover the type of pond liner material that works best, walk through a step-by-step process to calculate liner size using our pond liner calculator, and run through some important reminders and next steps as you construct your pond.

The Best Pond Liner Material (EPDM)

Ethylene Propylene Diene Monomer (EPDM) is a flexible material that can easily conform to any configuration you choose. When selecting a liner, make sure to get one that is meant for ponds. Unfortunately, some pond owners experiment with pool liners or roofing material, neither of which are effective solutions. These materials are often constructed with chemicals to reduce algae or mold that can be harmful to fish and may tear easily. Instead, stick with EPDM rubber pond liner. It is safe for fish, plants, and wildlife and is the ideal product for a natural look.

Pond Liner Calculation in Feet

To begin, obtain measurements (in feet) for the longest, widest, and deepest points of your pond. Next, plug these numbers into our pond calculator. For reference, or if you'd prefer to do the math by hand, we're using the following formula:

(Length + (2 x Depth + 1)) by (Width + (2 x Depth + 1))

Let's look at an example for a pond that is 10' long, 5' wide, and 3' deep and follow the formula one step at a time:

  1. Calculate double the pond's depth: 2 x 3' = 6'
  2. Add 1' extra for anchoring the liner: 6' + 1' = 7'
  3. Determine the liner length: 10' + 7' = 17'
  4. Determine the liner width: 5' + 7' = 12'

This means your liner would need to be at least 12' x 17'. Since EPDM liners are sold in precut sizes, purchase the closest size match (e.g. 15' x 20'). If in doubt when selecting a liner, opt for a larger one that will provide additional flexibility to work with or expand your project.

Reminder About Pond Liner Material

Once you've calculated the right pond liner size, don't forget that you'll need pond underlayment as well. Underlayment is a soft polypropylene non-woven fabric that protects your liner from rocks and other sharp objects. Underlayment is recommended for any surface where pond liner will be placed, but unlike pond liner, it doesn't need to be seamed. It's sold in sections that are 10' wide, so you can calculate the size you'll need with these steps:

  1. Multiply the length and width of your liner: 15' x 20' = 300'
  2. Divide by the width of the underlayment: 300' / 10' = 30'

In this example, your underlayment would need to be 10' x 30' to pair with your liner. When installing, simply cut it in half and you are good to go.

Next Steps

Now that you've mastered the pond liner calculator and have all of your measurements, head over to our video and step-by-step guide on How to Build a Pond. Great for visual learners, the guide includes tips for installing your liner, underlayment, and other pond equipment like pumps, waterfalls, and lights. If you have any questions or need additional help using our pond liner size calculator, our customer service experts will be happy to help.