A standard dose of Benadryl for dogs is one mg per pound or 2.2 mg per kilogram of your dog’s weight. If you prefer to use pounds, multiply the dog’s weight by 1 mg: dog’s weight in lb Ă— 1 mg. If you prefer to use kilograms, multiply the dog’s weight by 2.2 mg: dog’s weight in kg Ă— 2.2 mg.