TWO OPTIONS TO MEASURE YOUR HOT TUB COVER
You can either take the measurement directly on the cover if it is currently in good condition.
Take measures of your spa.
In either way, you must always take the external (outer seam to outer seam or furthest part of the acrylic to the furthest part). Since the manufacturer has a margin of error of 0.5 inches.
For more details see also our spa cover mesurement video!
it is not necessary to add 0.5 inches (and/or more) if you are confident with your measurements.