The force of a dog's bite is measured in pounds per square inch (PSI). The English Mastiff has the strongest bite at 556 PSI. Rottweilers, as well, have a strong bite force of 328 PSI, but not even close to the English Mastiff. The German Shepherd, often used as police dogs, has a bite force of 238 PSI. Placing close to the German Shepherd are the American Pit bull Terrier and the Dutch Shepherd, with bite forces of 235 PSI and 232 PSI, respectively.