Choosing the right accordion boot for your truck doesn’t have to be guesswork. At AccordionBoot.com, we’ve created a free, easy-to-use Boot Opening Calculator that helps you determine the exact perimeter of your window opening based on its shape — so you can order the perfect-fitting boot the first time.
Whether you’re working with a rectangle, circle, oval, or something in between, this tool eliminates the measuring confusion and helps ensure a snug, leak-proof fit.
Why Measurement Accuracy Matters
For an accordion boot to seal correctly, the window openings on both the cab and the camper shell or sleeper must be:
- The same size
- have some way to attach the boot by some type of thin wall or flange
- Within the accepted perimeter range for the boot you’re ordering
If the perimeter is too short, the boot may not seat properly. Too long, and it may sag or leak. That’s why our calculator is such a helpful tool.
How the Calculator Works
Our online tool helps you calculate the total perimeter length of your window opening based on the shape you select.
Step-by-Step Instructions
- Go to the Calculator:
https://www.accordionboot.com/Calculate-Measurements.php - Choose Your Shape:
Select from a list of common shapes such as:- Rectangle
- Circle
- Trapezoid
- Enter Your Measurements:
Input dimensions such as:- Height
- Width
- Diameter (for circular openings)
- View the Result:
The calculator will give you the total perimeter in feet — this is the length of boot opening you’ll need. - Compare Both Openings:
Be sure to measure both your truck cab and camper shell openings. They must be nearly identical for a good seal.
Pro Tips for Best Results
- Use a flexible measuring tape for best accuracy (especially for curved shapes).
- If you’re between sizes, round up.
- Don’t forget to also measure the gap distance between cab and camper shell — this affects the boot depth, and help determine which part number you need.
- Take note of whether your windows are sliding — if so, you may need a compression boot instead of a standard accordion boot.
Example Use Case
Say you have a rectangular window that’s 34 inches wide and 22 inches tall. Plug those into the calculator, and it will return a perimeter of approximately 112 inches. The calculator will round up to 10 feet.
You can then use this info to:
- Select the correct boot size
- Confirm compatibility between cab and shell openings
- Avoid ordering the wrong product
Ready to Order?
Once you’ve calculated the correct perimeter, head over to our product page and choose the boot that matches your measurements:
Still unsure? Just contact us and we’ll help you select the right boot based on your measurements.
Final Thought
The Boot Opening Calculator is one of the most important tools on our site — and it’s free to use anytime. If you’re sealing a cab-to-camper gap, a custom sleeper, or replacing an OEM boot, don’t skip this step.
Try the Boot Opening Calculator »
The Boot Opening Calculator helps you measure the perimeter of your truck cab or camper shell window opening to ensure a proper fit for an accordion boot.
Choose your window shape, enter the height and width (or diameter), and the calculator will return the perimeter measurement needed to find the correct boot length.
For a proper seal, both openings must be the same or very close in size. If they differ, modifications may be necessary.
Yes, the gap distance determines the boot’s depth. The calculator helps with perimeter size, not gap length.
If your truck or camper shell has a sliding window that can’t be removed, a standard accordion boot won’t work. You’ll need a compression-style boot instead.