HOW TO MEASURE YOUR DOG'S NECK SIZE
It's a really easy process. You wrap a measuring tape, or a piece of string if you don't have one, around the nape of your pets' neck. Then rest the tape/string where you would like the collar to sit. Then by tightening or loosening the tape/string, you can decide on where you would like it to rest on your dogs' chest. A gap of two finger widths space is recommended. This can be measured by placing two fingers under the tape/string at the nape of your dogs' neck.
Please watch the video to get a more accurate understanding of how to measure you dogs neck.
The method for sizing in this video applies to any breed dog. For example Dachshunds and French bulldogs all the way to Dobermans and American Pitbulls.