If your dog has an 18" neck and is full grown, we suggest a 16"-20" collar for a perfect fit. (We don't go by the total length of the collar) If your dog has an 18" neck and is still growing, 18"-22" is the best size collar to choose.
-If you do not have a tape measurement, use a ribbon or a shoe lace to wrap around your dog's neck. Mark where the two fingers meet and measure against a ruler.
***Our leather collars have 4 inches of adjustment, if you are still unsure, message us and we will get right back to you.