A dog safety vest is pulled over the head and fastened at the neck and below the belly, usually using continuously adjustable Velcro fasteners. It is just as easy to determine the right size for the dog safety vest. Depending on the manufacturer, either the length of the back or the circumference of the chest is used for the measurements. For the back, simply place a tape measure between the nape of the neck and the base of the tail and measure the distance, taking into account a margin of about one centimetre; the chest circumference is measured starting from the shoulders directly behind the front legs of the animal.
With a dog life jacket, you also need to take into account the weight of the animal. For safety, dog life jackets have safety straps with sturdy snap closures and a handle on the back for retrieving the animal.