My first supervising physician in pediatrics in 1993 taught me a quick and easy way to convert pounds to kilograms in your head when you are dosing by weight antibiotics for kids in the outpatient clinical setting. Subtract the first number from the total if the weight in pounds is two digits; subtract the first two digits as a whole number if the weight is three digits. Then subtract that from the total, and divide by half, which gives you the weight in kg.

Example 1: 57 pounds: 57 − 5 = 52

52 ÷ 2 = 26 kg (actual conversion, 25.9 kg)

Example 2: 113 pounds: 113 − 11 = 102

102 ÷ 2 = 51 kg (actual conversion, 51.3 kg).

As you progress to higher adult weights (150 to 200 pounds), the actual value can vary by a few kg, so it is not as accurate.—CATHERINE DOCOUS, PA, CNS, Oneida, N.Y. (219-3)

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