How to Measure a Portable Acrylic Spa for a Custom Replacement Hot Tub Cover

Ordering a custom hot tub cover is one of the easiest ways to protect your spa, improve energy efficiency, and extend the life of your hot tub. But a perfect fit starts with accurate spa measurements. Even small measuring mistakes can lead to gaps, heat loss, or a cover that simply doesn't sit right.

Follow this step-by-step guide to measure your portable acrylic spa correctly so your custom replacement cover fits snugly and performs exactly as it should.

Always Measure the Spa - Not the Old Cover

Never measure your old spa cover. Always measure the spa shell itself.

Over time, spa covers can:

• Shrink from sun and UV exposure
• Warp from moisture absorption
• Lose their original shape

Measuring an old cover often results in a replacement that's too small or uneven. Measuring the acrylic spa shell ensures your new cover fits properly and seals in heat.

Step 1: Measure Length and Width

Use a tape measure to:

• Measure the widest point from edge to edge
• Measure both the length and width
• Take measurements from the acrylic lip, not the cabinet or skirting

Write everything down to the nearest ¹/₂ inch unless your supplier specifies otherwise.

Step 2: Measure the Corner Radius (Critical for Fit)

Most portable acrylic spas have rounded corners, and the corner radius is one of the most important measurements for a custom spa cover.

What you'll need: a carpenter's square or any rigid square edge.

How to measure the radius:

1. Place the square snugly into the corner of the spa.
2. Slide it until both edges of the square touch the straight sides of the spa.
3. Measure the distance from the corner of the square to where it meets the curve.
4. That measurement is your corner radius.

Pro tip: If you're between sizes, always estimate slightly smaller rather than larger.

A smaller radius will fit better than one that's too large. Oversized corners can leave gaps where heat escapes.

Step 3: Measure Strap and Flap Lengths

The flap (also called the skirt) is the material that hangs down the sides of the spa.

To measure:

• Measure from the top of the spa shell down past the acrylic
• Ensure the flap fully covers the acrylic shell
• Round flap lengths up to the nearest inch

Rounding up helps with:

• Better wind protection
• Proper strap alignment
• A cleaner, more finished look

A flap that's too short can expose the acrylic and reduce insulation efficiency.

Want a Professional to Measure Your Spa?

If you're not comfortable measuring your spa yourself, our experienced service professionals can measure your spa in Milwaukee, Mequon, Port Washington, West Bend, Hartford, and surrounding areas for an additional cost.. This optional service is available to give you peace of mind knowing your custom spa cover is made to exact specifications.

We also offer:

• Spa cover delivery
• Professional spa cover installation
• Old spa cover removal and disposal

This is a convenient option for customers prefer not to transport a large, awkwardly sized box or lift a heavy cover.

Customer pickup is always welcome. Our retail team will help place the new cover into your vehicle, but customers are responsible for properly securing their load for transport.

Final Spa Measuring Tips

A properly measured spa cover fits better, lasts longer, and keeps your hot tub running efficiently. Whether you measure it yourself or rely on our experts to handle it, we're here to make the process easy.

Frequently Asked Questions About Measuring for a Spa Cover