How to Measure For a New Hot Tub Cover

If you’re reading this post, we’re guessing you’re probably getting ready to buy a new cover for your spa or hot tub. Insulated spa covers are a vital part of a healthy, efficient spa, so it’s an important investment. Before you can worry about choosing insulation level, color, or upgrade options your hot tub cover, you first need to figure out which size you need. The only way to do that is to measure your hot tub to ensure you’re getting the right fit.

The Importance of a Fitted Cover

A hot tub cover that’s too small allows heat and water vapor to escape. Especially in colder weather, you may find that a small cover won’t allow your hot tub to retain enough heat. Escaping steam and water vapor means you’ll be refilling the spa and replacing chemicals more often. Between the energy, water, and chemical losses, a cover that’s too small is costing you money on a daily basis. A small cover also leaves your acrylic shell exposed to the sun’s UV rays, which can cause it to fade and deteriorate more quickly.

A cover that’s too big can also leak heat and water vapor from under the edges, plus it can create a wet, sloppy mess around your spa or hot tub. Since the skirt around the cover can’t form a tight seal against the sides of your spa, those flaps capture condensation from the escaping vapor and drip water all around your spa. Again, this just costs you money on energy, water, chemicals, and now exterior spa damage over time. The extra overhang also increases the risk of cover damage from storms, animals, and daily wear and tear.

How to Measure for a New Hot Tub Cover

Before getting started, you’ll need to grab a few supplies:

If you don’t have a square, you can use a pair of straight edges or rulers instead.

There are a few different shapes of spas and hot tubs, and each requires a slightly different method of measurement. But with each method, the first step is to remove the existing cover and set it off to the side. We’re only going to be measuring the spa itself.

Remember to always measure to the exterior edge of the acrylic molding (including flare-out), not necessarily the wooden frame. Doing so can return a cover measurement that’s the wrong size. If your spa cabinet has a narrow top rail just below the edge of the acrylic, include that in the measurement.

Start by drawing your spa shape on a piece of paper. This is where you’ll keep track of the different measurements.

Measuring the cover skirt

Lay a carpenter square or straight edge along the top of the acrylic in a way that extends over the outer edge. Use a measuring tape to measure from the bottom of your straight edge to the edge of the acrylic. To accommodate for future shrinkage, round this measurement up by one inch. For example, if you measure 4”, you would want to buy a spa cover with a 5” skirt. If your current cover is in decent shape, and you're happy with the skirt length, you may also use your existing cover as a guide.

Measuring the safety straps

Use the same process used to measure the cover skirt in order to measure the length needed for your safety straps. From the underside of the straight edge, measure down to the top of the clip on your spa cabinet. This measurement should be at least 1” longer than your cover skirt measurement, if not more. Do NOT include the actual clip in your measurement. You are measuring for strap length only. Again, if your existing cover is in decent shape, and the straps are just the right length, you may use the cover as a point of reference.

IMPORTANT NOTE: Unless you buy your replacement spa cover from the same company each time, your cover straps on the new cover may be in slightly different positions. If this happens, simply adjust the placement of the clips on the spa cabinet.

Measuring a round hot tub

This one’s the easiest, and only requires one measurement: the diameter. Yep, that's it. If you have a perfectly round hot tub, just measure across the exact center of your hot tub.

The cover manufacturer will automatically calculate the circumference for you based on your hot tub's diameter, so make sure this measurement is 100% accurate.

Measuring a square or rectangular hot tub with straight corners

To measure a square or rectangle hot tub, simply measure the length and width.

If the measurements are not the same, pay close attention to which one is broken by the fold (usually the length measurement). When you go to enter your measurements in the online order form, you’ll need to put the numbers in the right places if you want the cover to fold the same direction it used to.

Measuring a square or rectangular hot tub with rounded corners

Same as above. Start by measuring the length and width, paying attention to which measurement has the fold if it’s not a perfect square. Next, you’ll need to measure the radius of your rounded corners. Grab your carpenter square or a pair of straight edges.

Once you have your measuring tools, set the straight edge or square against the outer edge of your acrylic. Measure from the inside edge of the square to the point where the curve ends and the straight line begins. This will give you the curve radius.

It’s best to be precise with this measurement. But if you have to round, round down. If you round the corner radius up, the cover will be too tight.

Measuring a hot tub with cut corners

If your square or rectangular hot tub has one, two, or even four cut corners, start with the total length and width measurements. Then measure the size of the angled corner.

Depending on the number of cut corners, you may need to also include one or two other measurements of the sides touching the corner(s). Pay close attention to the order form diagram when entering your measurements.

Measuring an octagon or hexagon hot tub

If your hot tub has either six or eight sides that are all the exact same size, start with a total length measurement. Next, record the measurement of an individual side.

Pay close attention to the diagrams when ordering your hot tub cover, as some require total length and a side length, while others just require a length and width measurement.

Measuring an unusual or oversized hot tub

For unusual shapes, unique applications or features, and sizes bigger than 96” long or wide, you’re looking at a special order cover. An example of this might be a replacement cover for a swim spa or a large inground hot tub. All custom spa covers are technically made to order, but these types of covers require more precise data inputs. If you have a cover that fits into this category, one of our customer service representatives can help you complete your order. All you have to do is fill out the online form to request a quote.

Common Mistakes

The most common mistake we see is when spa owners measure their old cover instead of measuring the spa itself. In some cases, this may work out just fine. However, as covers age, they tend to warp and the vinyl can shrink, which may give an inaccurate reading. When a customer buys a brand new spa cover, and it arrives one or two inches either too large or too small, we often find that they measured the old, misshapen cover. Avoid this problem by measuring your hot tub according to the steps above!

When measuring, it’s best to be precise. However, for length, width, and diameter measurements, some manufacturers recommend adding an inch to the total measurement. This allows ½ inch of wiggle room on each side, as some covers shrink a little bit over time.

If you have any questions or need help with purchasing a new custom hot tub cover, call or stop by your local Leslie’s store to speak with one of our knowledgeable pool and spa professionals. You can also check out our Hot Tub Cover Buyer's Guide for more information about the next steps.