One of the more difficult things for many people, is trying to measure a cut-corner when the corner is also rounded. There are numerous ways one may go about figuring this measurement, but this is the easiest we have found so far.
Using masking tape, simply extend the lines of your spa (or existing cover) as shown below. Where the tape crosses is where you want to measure from. In the diagram below, “A” is the measurement of the cut-corner. If you don’t have any tape, a yardstick (or other small piece of wood) will also work.
The diagram below shows the pitfalls with mis-measuring a cut-corner. The green line represents a measurement too large while the red line represents a measurement too small. As you can see, with too large a cut-corner the cover wont completely cover the spa. Too small a cut-corner and the cover simply overhangs a bit. If in doubt always go with a slightly smaller measurement. The cover may be slightly large and overhang the corner a bit, but it will cover the entire spa…… and no one but you will ever know.