I often need to convert pounds to kilograms when calculating pediatric doses. To do so, subtract the first digit of the patient’s weight from the total number of pounds and divide by two.

For example, if a child weighs 46 lb, subtract 4 (the first digit) from 46 (the child’s weight in pounds). This gives you 42. Divide by two to get 21 kg. It works every time! This is faster and easier than trying to divide by 2.2 quickly in your head or having to look all over for a calculator. — Debra Mallory, RN, PhD, NP-BC, Terre Haute, Ind. (156-10)

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