A homeowner putting in a do it yourself pond or a water feature that incorporates a pond needs to know how to calculate pond liner size. Here are a few calculation tips to help the job go smoothly.
Calculating Liner Size
As many ponds are not perfectly square you will need a liner that will cover all the contours and crevices of your pond with a one foot margin around the edges. In order to get accurate measurements from an odd shaped object you will need to take your measurements at the longest, widest, and deepest points in your pond. Using these figures will help to ensure that the liner you order will be large enough.
To find the length of the pond, determine the longest span in feet and use this as your measurement. For width, find the furthest point at a 90-degree angle from the first measurement. The location of your measurements should create a cross or a large ‘X' at some point on the pond's surface. Finally, measure the depth from the very deepest part of the pond to the top of the pond.
Length=Max Length' + 2x Depth' + 1'.
Width=Max Width' + 2x Depth' +1'.
Example: A pond with a maximum length of 6 feet and a maximum width of 10 feet that is 3 feet deep would require a 17' x 13' liner.
Width: 10' + 6' + 1'=17'
Length: 6' + 6' + 1'=13'
Calculating Volume of the Pond
Unlike the measurements for the liner, you will need to measure the AVERAGE length, width, and depth of the pond to get an accurate volume calculation. To find the average length, take three individual measurements at different spots along the pond including the longest. Add the results together and divide by three to get an average. Do the same for both the width and the depth. Now that you have your averages, multiply them together and multiply that answer by 7.48 to get the volume of your pond. You can use four or more measurements if your pond is a larger size, just make sure to divide by the same number after adding them.
Example: A pond with an average length of 6 feet and an average width of 10 feet that is an average of 3 feet deep would be 1347 gallons in volume.
6' x 10' x 3' x 7.48 = 1347
Take your measurements to your professional pond liner dealer who can double check your calculations and can give you advice on the best type of liner to use to suit your unique situation.