How to Measure for an Inground Pool Liner

100ft-measuring-tape for A-B measuring a pool for a custom cover

“I don’t think I need to measure, my pool is just a standard size." Unfortunately, there is no such thing as “standard” when it comes to measuring for in-ground pool liners.

The reason for this is that there are so many different styles and shapes of pools, and even mass-produced in-ground pool kits may not always be installed exactly to plan as a result of conditions in each yard.

Because of all the different pool types out there, very few retailers will stock in-ground pool liners; they will almost always be custom made, so providing accurate measurements is critical.

The specific measurements you’ll need to provide will depend on the shape of your pool, but every set of liner dimensions will need to include the length and width of the pool, corner type, wall height and deep-end depth, and bottom contour dimensions. I’ll be discussing some helpful measuring tips that will apply to most pool owners, but for detailed specifications and directions of what measurements are required for your specific pool shape and the form to submit, refer to our specific and easy to follow in-ground liner measuring form, Liner Measuring Made Easy.

Measuring Your Pool's Length & Width

how to get an accurate measurement of length and width of your liner

Width and length measurements are pretty simple to take; you just need to measure the longest and widest points of the pool. The biggest thing to keep in mind is to make sure that the measurements are taken at the bead receiver (where the liner snaps in to the track) and not at the edge of the coping.

As you can see in the image, taking the dimensions from the pool deck or the coping could result in a difference of several inches, which is huge when it comes to in-ground liner measurements. The diagram points to two places because in some instances pools will have tile borders running across the top and the liner will snap in to a track that is underneath that border. The important thing is to take the measurements from the bead receiver, wherever that may be.

Measuring Corners

how to measure cut corners on an inground pool

Next, you should identify the corner type you have on your pool. They will either be 90 degree (square), cut, or rounded. If your corners are square (90 degrees), no additional measurements will be needed. If you have cut corners, you’ll simply measure the length of the corner, as shown in the image.

Rounded or radius corners must be squared off before measuring. Use two straight edges, like measuring sticks, to form a square corner, as pictured by the dotted lines in the picture below. Mark the corner you create as point 1, and the break in the curve of the pool where it begins to straighten out as point 2. Measure the distance between point 1 and point 2 for your radius corner measurement. Radius corners on in-ground vinyl liners can range in size but are usually somewhere around 6 to 12 inches.

how to measure radius corners

Measuring Your Pool's Floor

Most in-ground vinyl pools do not have a flat bottom, they have a shallow end and a deep end. So, you’ll need to measure the shallow end wall height (which should be the same as the depth of the shallow end) and the overall depth of the deep end. As with the overall length and width measurements, it is extremely important to take depth measurements from the bottom of the deep end to the bead receiver.

In some pools, there will be a slight slope in the shallow end. Sometimes it can be a very gradual, hard to notice slope, but it could impact the fit of your new liner. For this reason, you will also need to provide the depth where the shallow end stops and the slope to the deep end begins, known as the "break." This is measurement C1 in the diagram below.

How to measure bottom contour of inground vinyl linersThe next set of dimensions you need to provide are horizontal measurements of the bottom of your pool. The measurements you need will vary based on the type of bottom contour your pool has. In the diagram above you can see four bottom contour types: standard hopper (the most common), constant slope, wedge, and safety ledge.

homemade plumb bob - pole, string, weight - for measuring pool depth

Though it may not look like it, you can take these measurements pretty easily with water in the pool. You’ll need a long straight pole (the tele-pole you use to skim the pool is perfect), a long enough piece of string to reach the bottom of the pool, a small weight you can tie to the string, and of course measuring tape. Tie the weight to the string, and then attach the string to telepole.

As you can see in the diagram, each measurement you need to take is labeled with a letter. We’ll use some measurements on the standard hopper as an example for how to measure the bottom contour. Use the pole with the weighted string you’ve created to find various points at the bottom of the pool and measure from the pool wall/bead receiver straight across to the string.

For example, to take measurement “D”, find the shallow end break with your pole (make sure the string hangs straight down so there is no slack) and measure the distance from the shallow end wall to the string. As mentioned above, all of these dimensions are taken horizontally, you will simply measure the straight distance between two points, even for the slopes.

You will never measure any of the slopes on an angle. So, for measurement “G”, you will again use the pole to find the point where the flat part of the deep end stops and the slope up to the deep end wall begins, and you will measure from the deep end wall straight across to the string.

Because all of these measurements are taken horizontally, all of the individual measurements of your bottom contour should add up to the overall length and width of your pool. For length, measurements D+E+F+G should add up to be equal to the overall length of your pool. For width, measurements H+I+H (“H” being the slopes on each side of the pool) should add up to the overall width of the pool. If they don't add up, try again. Each measurement should begin exactly where the previous measure ended.

In the diagram labeled Right, you can see that because the measurements were taken horizontally, they add up to the overall width of the pool. In the diagram labeled Wrong, the actual slopes were measured and so when you add all the dimensions up they turn out to be more than the overall width of the pool.

Right and Wrong ways to measure inground pool liners

For most pools, there will still be a few more measurements you need to take around the perimeter of the pool, and those will vary based on your specific pool shape. If you have stairs that need to be covered by the liner, you’ll need to measure those completely as well. Please refer to our in-ground liner measuring form to double check that you have taken all of the necessary measurements.

Now comes the fun part: Take a look at our variety of in-ground vinyl liner patterns and gauges so you can provide us with a few of your top choices for quoting purposes. Visit our in ground pool liners page and click on each of the manufacturers to view the patterns they have available. Submit your measurements and your pattern choices to us, and one of our in-ground liner experts will give you a call with a quote within a day!

In The Swim makes every effort to provide accurate recommendations based upon current ANSI/APSP/ICC-5 2011 (R2022) standards, but codes and regulations change, and In The Swim assumes no liability for any omissions or errors in this article or the outcome of any project. You must always exercise reasonable caution, carefully read the label on all products, follow all product directions, follow any current codes and regulations that may apply, and consult with a licensed professional if in doubt about any procedures. In The Swim assumes no legal responsibility for your reliance or interpretation of the data contained herein, and makes no representations or warranties of any kind concerning the quality, safety, or suitability of the information, whether express or implied, including, without limitation, any implied warranties of merchantability or fitness for a particular purpose.