But what if you just have the watch case and the watch band itself is gone? Don’t worry, you can use this guide from to help you successfully measure a for a watch band without actually having the watch band. Without those two measurements, you will not be able to ensure that you have the right size watch band for your watch case. One of the most important things to do when you are planning to change your watch b and is to measure the existing band (if possible) and find out the width and length.