To measure your RV shower door opening accurately, focus on the finished opening rather than the shower pan depth. For height, place your tape measure at the lowest flat point inside the shower pan where the door will sit, then measure straight up to the top of the opening. Take measurements at three points—left, center, and right—and use the smallest value as your door height. For width, measure wall to wall where the door will mount at the top, middle, and bottom. Again, use the smallest measurement for your door width. Avoid guessing the pan depth or measuring outside the shower. Using the smallest measurements ensures the replacement door fits properly. This method guarantees you order the correct RV shower door replacement with confidence.