Knowing your dog's exact size is vital if you wish to buy it properly fitted clothing. It also can help you figure out how your dog compares to others of its breed. Measuring your dog from the tip of its nose to the tip of its tail gives you its literal length. This number, however, is not what you need to provide when asked for your dog's length. If you were to try to order your dog a coat based on a nose-to-tail-tip measurement, for example, it would be far too large.
Coax your dog to stand up as straight as possible. You will not achieve an accurate measurement if your dog is laying down, sitting, sniffing the ground or doing anything other than standing straight.
Place the tip of your tape measure on your dog's spine at the point on its neck where its collar rests. Hold the tip in place with one hand.
Lay the measuring tape straight across your dog's back, following its spine, until you reach the point where its tail meets its body.
Read the measurement on the tape where your dog's tail begins. This measurement -- which is significantly less than the nose-to-tail-tip measurement would be -- is your dog's length.
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Morgan O'Connor has been writing professionally since 2005. Her experience includes articles on various aspects of the health-insurance industry for health-care newsletters distributed to hospitals as well as articles on both international and domestic travel.