Calculating weight loss of newborns? You can get reaaaally good at doing it on your own: (Birth weight - Current weight) / Birth weight * 100 = % lost. Or you can find a website to do it for you.
The first way can solidify your admittedly weak arithmetic skills. But the second way is so easy!
And that's your tip of the day, and possibly of the week since I have been too busy with work + Fourth of July + life to be posting much. I promise the next installments of my MPH series are in the works!