To measure your Hot tub or Spa, always measure the top of your Spa and not your previous cover. Old foam covers tend to shrink or expand over time due to the different conditions they have been under. Please make sure to provide measurements in inches not in feet.
For measuring your corner radius you will want to use either a framing ruler or two regular rulers to get this dimension. Using one of the two options you will need to measure where the spa begins to curve as shown in the pictures below. 
Please make sure that all of your corners have the same radius to assure that the new cover will fit.
For kidney bean or other odd shapes we may require you to make a template. Please follow the following instructions to make a template.
One of the best materials for hot tub owners to use in making a template is a piece of clear plastic. Clear plastic painting drop cloths work great and are relatively inexpensive.
1. Carefully stretch the plastic across the hot tub or spa, making sure it’s taut with no wrinkles. Using thumb tacks or tape hold the plastic securely in place.
2. With an indelible sharpie marker, carefully trace the outline of the desired cover. Remember, the cover will be made to the shape you trace and we’ll straighten out any waviness in the lines! DO NOT trace the opening of the spa, or the cover will fit inside the spa!
For in-ground/concrete spas, the cover should overlap the edge of the spa at least 2″. Any more overlap will lessen the chance of the cover falling into the spa when being put back on.
3. Draw a dotted line to indicate the direction and approximate location of the fold. We’ll center the fold on covers that are up to 8′ across. Larger covers will be in two pieces, with each piece folding in half.
4. While the plastic is still stretched across the spa, write your name, phone number and “This is the TOP” on the top surface of the plastic, so we’ll know which side is up and to avoid any confusion over what side is the top and what side is the bottom of your cover.
5. If you only want a partial skirt, please indicate its location and length. If you don’t want a skirt or the skirt encompasses the entire perimeter of the spa cover, this can be omitted from the template.
6. Indicate the location of any handles and the location and length of any tie-downs.
After we receive your hot tub or spa cover template, we’ll create a CAD drawing and email it to your for revisions and approval.
If you know that your spa will require a template, please email us at customercare1@rhtubs.com for more details.