Step 1 - Measure Dog's Neck: Using a (soft) sewing tape, measure around your dog’s neck where their collar normally sits. Pull the tape until it is snug but not tight. You should be able to comfortably put two fingers between the measuring tape and your dog's neck. Record this measurement, it will be the primary factor to consider when selecting a size.
If you do not have a soft tape, use a piece of string (or similar) and measure around your dog’s neck using the above instructions. Lay the string flat and use a ruler or tape measure to obtain the measurement.
Step 2 - Measure Dog's Head: If you are ordering a standard martingale (without a buckle), the collar will need to comfortably fit the dog's neck, but also adjust to be large enough to fit over their head and ears. Using the same method from Step 1, measure the head starting at the throat and going over the ears.
Record the measurements and use while determining the correct size collar to order.