How To Measure a Hot Tub Cover
Ordering a new hot tub cover shouldn’t be stressful. At Imperium Covers, we build every custom hot tub cover to your measurements!
Before You Start: A Few Ground Rules
To make sure your hot tub cover size is accurate:
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Measure the tub, not the old cover. Old covers swell, warp, and lie. Always measure the acrylic shell wherever possible.
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Please provide measurements in inches. The hot tub cover industry builds in inches; it keeps things simple and consistent.
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A little bigger is better than too tight. Rounding up by about ½–1" total gives you a cover that drops on nicely instead of fighting the lip of the tub.
What You’ll Need
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Tape measure (inches)
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Notepad (or your phone)
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Two straight edges (rulers) or a framing square for corners
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Optional: a second person to hold the tape
That’s all you need to measure your hot tub for a new cover.
Step 1 – Figure Out Your Hot Tub Shape
Look at your hot tub from above. It will be one of these common shapes:
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Square or rectangle (with sharp or rounded corners)
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Round/circular
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“Other” (octagon, kidney shape, speakers sticking out, raised back, etc.)
Your hot tub shape decides which measurements matter most for your custom cover.
Step 2 – Measure Length & Width (Square / Rectangular Tubs)
For standard square or rectangular hot tubs, you mainly need two core numbers: length and width.
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Measure the length, the longest side of the acrylic shell, outer edge to outer edge.
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Measure the width, the shorter side, outer edge to outer edge.
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Round up, not down
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If you get 78 ⅜", round to 78.5" or 79", not 78".
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Add about ½" of wiggle room so the cover doesn’t sit too tight on the shell.
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These are the numbers we build from at Imperium Covers when we manufacture your custom hot tub cover.
Step 3 – Measure Corner Radius (If Corners Are Rounded)
If your hot tub has rounded corners, you’ll need the corner radius:
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Put two rulers together to form an L-shape.
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Place that L snug against the straight edges of one corner.
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Measure from the inside corner of the L to where the tub starts to curve.
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That distance is your corner radius.
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Check another corner to be sure it matches.
If your corners don’t all behave the same, snap a couple of photos of the tub and send them to us. We’ll help you out before we build your replacement cover.
Step 4 – Measure a Round Hot Tub
If your tub is perfectly round, measuring your hot tub for a new cover is straightforward:
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Measure straight across the center of the tub, outer edge to outer edge.
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That number is your diameter.
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Round up slightly (same rule: a hair bigger is better than too small).
Give us that diameter and we can handle the rest when we build your round hot tub cover.
Step 5 – Measure Skirt Length (The Hanging Flap)
The skirt is the flexible vinyl that hangs down from the cover and hides the shell lip.
To measure skirt length:
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Measure from the top of the acrylic shell down to just below the shell lip.
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That number is your starting point. Most people end up in the 3–6" range.
This helps us size the skirt so your custom hot tub cover looks clean and helps block drafts.
Step 6 – Hinge / Fold Direction (Simple Sketch Method)
Covers usually fold in half, so please let us know which way. The easiest way to explain this is with a simple sketch:
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On a blank page, draw your hot tub from above as a simple box or circle that roughly matches the shape.
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Draw a line where you want the cover to fold, write “Hinge” on that line, and add a small arrow showing which way it opens.
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Write your length and width along the sides of the sketch, and add the corner radius if your corners are rounded.
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Take a clear photo of the sketch and send it with your order so we can build the cover exactly how you see it.
This sketch removes almost all confusion about fold direction and how your cover should sit on the tub.
Step 7 – Weird Shapes, Speakers, and Cut-Outs
Please let us know if your spa has any non-standard features that affect the cover shape:
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Speaker pods
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A raised back or spillover
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A non-standard “kidney” or angled shape
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Anything that sticks above the shell
The more detail you provide, the better we can tailor your custom replacement hot tub cover to your spa.
Why We’re So Upfront About Measurements
Custom hot tub covers are made specifically to your measurements. If the measurements are off, the cover will be off.
That’s why we’re transparent about the process and why we encourage questions. We’d rather help you measure once, properly, than have you end up with a cover that doesn’t fit.
At Imperium Covers, we’re here to help you with any questions or concerns you have while measuring your hot tub for a new cover.
Quick Measurement Checklist
Before you order your Imperium Covers custom hot tub replacement cover, confirm you have:
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✅ Shape (square, rectangle, round, or other)
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✅ Length & width (inches, rounded up slightly)
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✅ Corner radius (if corners are rounded)
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✅ Skirt length
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✅ Hinge direction (shown in your sketch)
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✅ Notes/photos for any unusual shapes or features
Once you’ve got that, you’re ready to order your custom hot tub cover!