Maybe I wasn’t clear (sadly too often), i meant that it seems that the human tablets one does not need to vary the dosage per one’s weight, as in horse paste. Amirite?
The "correct" dosage is determined by your body weight. With the horse paste, you can attempt to match it exactly. With pills -- unless you start chopping them up -- you can only match approximately. But it doesn't matter. Ivermectin has very low toxicity, so -- as LittleLinda has pointed out -- you can safely take more than the "correct dose".
If the calculation says you need 15 mg, take 2 pills or 1.5 if you like to cut pills in half, but don't worry about the slight overage. Even 10 pills won't hurt you, but it would be a huge waste.