How to Measure Hot Tub Covers

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You need a new hot tub cover. Maybe you have needed it for months or even a year. But the thought of having to measure your hot tub in order to order the right fit is holding you back. What measurements do you need? How to measure the hot tub cover radius? Do you have to add an inch to your measure to be certain your cover will fit?

Because there are many models of hot tubs, all different in size and shape, you can’t simply buy a hot tub cover off the shelf and wish for it to fit on your hot tub. You have to measure it, and measure it precisely. Follow this guide to measure your hot tub the right way and and to find the order the perfect spa cover.

This guide will help you measure Hot Tub Covers and Spa Covers so that they will fit perfectly on your hot tub or spa. Even if a hot tub or cover manufacturer has your spa or hot tub on file, take the time to measure and be sure.

Make Sure your Cover is the Right Size

You have to be careful when measuring your hot tub for a new hot tub cover. If the cover is too big, you’ll end up losing water from condensation and you’ll have to go through the process of adding water to your spa, then wait for it to warm up.  Also, the cover could easily break on the edges, or the wind can lift the cover off your tub and you’ll have no more protection for your investment. If the cover is too small you can lose heat, you won’t have a proper seal, and the acrylic will not be protected.

Most hot tubs today are either square or rectangle in shape with radius corners. The radius corners is what gives most hot tub owners the shrills. Don’t worry, this guide will help you to measure your hot tub cover radius. Although these are the most common shapes of hot tubs we will go over all the other hot tub shapes as well so everyone will be covered.

How to Measure your Hot Tub

If you have any permanent add-ons, like speakers or a waterfall, you have to include them into your measurements. If you don’t, these parts won’t be protected.

If you already have an old hot tub cover, it’s better if you take your measurements directly on your hot tub. Why? Because if it’s an old cover, the chances for it of being loose are high. And let’s be honest, if you change your old cover, it’s probably because there is a reason for it. So don’t measure your old hot tub cover.

For all hot tubs, it’s best to measure your actual hot tub instead of the old hot tub cover. You have to measure from one extremity of the acrylic mold to the other. If you have a wooden frame, do not measure the wooden frame. Your hot tub cover would be too large.

Here at The Cover Guy, we suggest adding an inch to your overall dimension to allow for an easy fit on your hot tub. So if your measurement is 77” make it 78” so you have ½” per side wiggle room. Do not add anything to your radius measurement, that has to be precise. If anything, round down. So if your radius is 5” you can get away with 4” radius, but a 6” radius will make your hot tub cover to tight. Also, we recommend you draw the shape of your spa, including the radius, and write down the measure on it.

measure hot tub covers

How to Measure the Radius of a Hot Tub

hot tub radius measuring guideThis is the one that makes everyone worried. As the diagram shows the easiest way to measure a radius is with a carpenter square. The dimension needed is from the start of the bend to the imaginary point of the square if the tub was actually square. Rule of thumb is smaller is safer than larger. The smaller the radius the more square the corner of the hot tub cover.

Square or Rectangle with a radius on four corners
To measure radius “C”: extend straight lines indicated in red by laying straightedges against the sides of the spa. Measure from point “Y” to point “Z”.

How to Measure the Skirt of a Hot Tub

The skirt is the flap that hangs from the bottom of your cover. The skirt is really just cosmetic but if not measured correctly can cause some problems because if it is too long it will bunch and push your spa cover up. For wood rails as in the picture above measure from the top of the wood rail to the top of your spa acrylic. If anything you want to be a little short rather than long so the skirt does not bunch. If you do not have a wood rail then you want to measure from the top of the spa to the bottom of the spa lip and add 1/2″.

Common Shapes of Hot Tub

Circular hot tubs

  1. Measure the diameter and add 1/2″ to the dimension.
  2. Measure the skirt length.

Yay, you don’t have to measure any hot tub cover radius!

The circular hot tub is certainly the easiest one to measure, with only 2 measures to take : the diameter and the length of the skirt.  The diameter is the line from the very outer edges of the acrylic surface, including any flare-outs. Try to get this measurement in the very middle of your hot tub, right where the seam should be.  The length of the skirt is the measurement from the top of the acrylic mold, to the top of the wooden rim.

Square and rectangular hot tubs

  1. Measure the length and width of your hot tub, through the center or along the edges. Add 1/2″ to each dimension.
  2. Measure the skirt length.

Technically, a square hot tub will have both side equals. However, we recommend you measure both sides, just in case they aren’t equal. For a rectangular hot tub, make sure you request the fold direction you’d like. Most companies will by default cut the longest of the two sides in half.

Square and Rectangle Hot Tub with Radius

These are the same as the regular square and rectangular hot tub covers, except that they have rounded corners, more known as radius. Measuring your hot tub cover radius is rather easy. All you need is a carpenter square or two straight edges. Put them at an 90° angle at the corner of your spa. The radius is where the edge first touch the spa.

  1. Measure the length and width through the center.
  2. Measure the corner radius.
  3. Measure the skirt length.

Octagon Hot Tub 

  1. Measure from lip to lip and add 1/2″ to the dimension.
  2. Measure one panel of the octagon from point to point.
  3. Measure the skirt length.

Don’t forget that regardless of the shape your spa, you should measure from lip to lip, or the outside dimension of the acrylic which is the same as lip to lip. after you have a lip to lip measurement you may add up to 1/2″ on both length and width. This will give you a 1/2″ of play all around your spa cover.

Custom shaped hot tubs

Most of these covers will require you to measure hot tub covers and spa covers and also send a template provided by you to complete your cover properly. This would include spas with speaker bumps, waterfalls, or cut outs for rails or controls. For more unusually shaped covers, especially asymmetrical ones, your dealer or manufacturer will likely provide a template, or will have the necessary measurements on file. Some company only make regular shaped cover. Here is a good example of a custom oversized cover made by The Cover Guy.


Adding a cover to your hot tub is essential. It’s important to measure it precisely. When in doubt, re-measure. To sum up, here are the important points to remember when measuring your spa :

  • Take the measurements on the acrylic mold (diameter or length and wight).
  • Measure the radius (usually by multiple of 2 : 2 inches, 4, 6, 8 10, 12).
  • Decide on the axe you want the cover to fold. That axe will be measure A when you order.
  • Decide on the length of the skirt.
  • For every measures, round up to the nearest inch

Remember that you can always contact us if you need any help.

Email us at or call us toll free at 1-866-652-6837. There is always a hot tub cover specialist here to help you. The Cover Guy has every hot tub measurement on file so we can always matchup your hot tub with the proper dimensions. Be sure to know the brand and model of your hot tub.

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