Pounds to Kilograms

Hospitals and pharmacies are the most important case. Drug doses, anesthesia and IV fluids are calculated per kilogram of body weight, and patient-safety groups such as the Institute for Safe Medication Practices recommend that weight be recorded in kilograms only. A weight of 180 lb entered as 180 kg would make a dose about 2.2 times too large, so many US clinics now weigh patients on kilogram-only scales instead of converting at the desk.

Birth weights are another everyday case. US parents announce babies in pounds and ounces, while relatives abroad and most medical charts outside the US think in kilograms. A 7 lb 8 oz newborn is 7.5 lb, which is 3.40 kg; 8 lb 2 oz is 3.69 kg. Travel and fitness bring the rest: visa medicals, international race entries and online forms often accept kilograms only.

American gyms load bars in pounds: a standard 45 lb bar is 20.41 kg, so it is a little heavier than the 20 kg bar used in weightlifting competitions. One 45 lb plate on each side gives 135 lb, which is 61.23 kg, and 225 lb, the classic two-plate lift, is 102.06 kg. If you follow a program written in kilograms in a pound gym, convert the target load and then round to what you can actually build with the plates available.

Because the pound has been defined since 1959 as a fixed fraction of the kilogram, both kinds of plates are traceable to the same standard. Since 2019 that standard is the Planck constant rather than a metal cylinder in France, but the 0.45359237 factor did not change.

Pounds and ounces are not a decimal. 10 lb 8 oz is 10.5 lb, because there are 16 ounces in a pound; typing 10.8 adds about 0.14 kg that is not there. Convert the ounces first (divide by 16) or use the unit converter in ounces.

For a quick mental figure, halve the pounds and take off 10% of that: 180 lb becomes 90, minus 9, which is 81 kg against the exact 81.65 kg. To go back from kilograms, use the kilograms to pounds page.