Calculating the body mass index (BMI) of your dog is an important step in understanding their overall health. The fastest way to calculate your dog 's BMI is to use a calculator specifically designed for this purpose. These calculators are available online and can provide you with accurate results in just a few seconds. All you need to do is input your dog's weight and height, and the calculator will automatically generate their BMI number. It's important to note that this number is just an estimate , as there are many factors that can affect a dog's BMI such as diet, exercise, and overall health. However, using a calculator is still the fastest way to get an approximate idea of your dog's BMI and it can be useful when tracking changes in their health over time.