Weight Converter
Most pediatric medication doses are calculated in milligrams per kilogram of body weight (mg/kg) rather than by age alone, since a child's metabolism and body composition change quickly during growth. Getting the kilogram figure right is often the first step toward a safe, accurate dose — convert a weight below, then use our physician dosage calculator or OTC dosage calculator to work out an actual dose.
Why weight-based dosing matters
- U.S. scales read pounds; dosing charts use kilograms. Most home scales and pediatric growth charts in the U.S. display weight in pounds, but medication package inserts and prescribing references almost always specify dose in milligrams per kilogram — so an accurate kilogram figure matters even if you only ever see your child's weight in pounds.
- Small errors compound. Because doses scale directly with weight, a rounding mistake when converting can shift a dose meaningfully, especially for infants and toddlers where a pound or two is a larger share of total body weight.
- Use a recent weight. Children's weight changes quickly. Use a weight taken within the last few weeks — not one from several months ago — when calculating a dose.
Why an accurate weight matters
Because most pediatric dosing is figured from body weight rather than age, an accurate kilogram figure is often the very first step toward a safe dose. A weight that's off by even a small amount, or one that's simply out of date, can shift a calculated dose enough to matter, especially for infants and toddlers where every pound is a larger share of total body weight.
How to convert
Kilograms and pounds are just two different scales for measuring the same thing — one kilogram equals a little more than two pounds. Enter a weight in whichever unit you have, choose the unit you're converting from, and this tool does the arithmetic for you. It's worth converting rather than estimating, since medication references and prescribing information are almost always written in kilograms even when a home scale displays pounds.
Getting a reliable weight
For the most consistent readings, weigh your child at a similar time of day, in similar clothing, and on the same scale when possible. A weight taken at a recent well visit is usually the most reliable source, since clinic scales are checked regularly for accuracy. If you're weighing an infant or toddler who won't stand still, weighing yourself alone and then holding your child and subtracting the difference is a reasonable home approach.