Measuring a spa cover is not as easy as it seems. It takes some time and usually requires at least two individuals. It is important to measure your spa correctly otherwise the cover will not fit properly and will end up a big waste of money. It is difficult to determine exactly how to measure your spa cover especially if your spa is a circular or octagonal shape. Fortunately, there are a few formulas which work effectively regarding some of the most common shapes.
A square hot tub is fairly easy to measure. Simply measure the length and width of the spa - measure it twice just to make sure you did it right the first time. After you have measured the length and width you will want to add a couple of inches to your measurements, just to make sure it's not too small. A cover that is too large will be more effective than a cover that isn't large enough.
Measure your rectangle spa exactly the same way you would measure a square model. Length times width.
Measuring a spa cover for a round hot tub is more difficult than measuring a basic square or rectangle model. To measure a circular spa you will have to calculate the radius of the circle. The key is finding the diameter of the circle. It is very important that you do not make the radius too big. Unlike most other shapes where bigger is better, if you measure the radius too big, the cover will not fit over the circle's corners. If you measure it too small, it will be fine.
The easiest way to ensure you're measuring your spa cover correctly is to carefully measure all sides of the spa. As long as you measure the sides correctly, and add a few extra inches for room, chances are your spa cover will fit fine. A number of advanced spa covers are available with tie down locks which can be attached to either the deck or the wood on the spa.
If you are having difficulties measuring your spa cover, contact the manufacturer. They will be able to provide you with more extensive information regarding how to perform this task correctly.