How to Measure a RADIUS  Measure the radius by placing a carpenter's square on the outside of your spa or existing cover. The distance between the corner of the carpenter's square and the place where it TOUCHES the spa (A) equals the radius of the curve (see diagram). The measurement for (B) should be exactly the same. The standard radius is between 5 to 9 inches. Another method to determine the radius of your spa's corners is to take a sheet of paper and trace around one of the curved corners of your spa or existing cover. Remove the paper and by freehand (or with a divider/measuring compass) complete drawing the full circle. Then measure across the middle of the circle you drew, and divide by 2. This number is the radius. The standard radius is between 5 - 9 inches. The key is to NOT make the radius too big. If you measure the radius too large, it WILL NOT cover the radius corner. However, if you measure it too small, it will be just fine. It may hang over slightly but there will not be a noticeable difference. When in doubt, use the smaller measurement. The smaller the radius measurement, the larger the cover will be. The larger the radius, the more the cover will be "cut off". You can also utilize this Radius Template to help determine the correct radius measurement. Radius Template. If you are still unsure or not confident, you can always trace the existing corner of your existing spa cover and fax a copy to us. You can fax it to 856-804-1704. Please write your name and order number on the fax. Radius calculator |