E.g. If a medicine states:
The recommended dosage rate is 15 mg per kg bodyweight, equivalent to 1 ml per 10 kg bodyweight to be repeated once after 48 hours. In the calculator you would type "1" in the "Dosage (ml)" input, "10" in the "Per Body Weight (kg)" input and add the estimated weight of the animal i.e. "550kg". This would give us "55.0 ml".