For those who don't know, the bridge distance can be defined as the space or gap between the inside of one lens to the other. This is a very important number to get right. Should you happen to measure it incorrectly, then the bridge size can make for a very ill-fitted pair of stylish sunglasses.
A small bridge might tweak your nose, which may cause your glasses to sit too high on your face, whereas an oversized bridge will cause the frames to glide down your nose bridge. Once again, the easy way to get this measurement done is by checking a pair of sunglasses you already own. The bridge distance is the second number in this regard. The estimation will help you know at least which glasses should you consider if you haven't previously owned any.
Here's what you can do, get something flexible like – a twist tie and bend it diagonally on the top of your nose bridge. Remove it and use tape or ruler to measure the distance between the segments where the bridge or pads will sit. If you don't have a pair of old sunglasses, it would be better to schedule an eye doctor appointment, and s/he will help you get an accurate measurement. The fun will begin when you have the size in hand.