Lbs to Kg Converter

A pound (lb) is a unit of weight used in the United States. A kilogram (kg) is the unit used in science and medicine. This converter turns a weight in pounds into kilograms, so your number matches the form or scale you need.

What Pounds to Kilograms Conversion Measures

This tool changes the unit, not the weight. 150 lb and 68.04 kg are the same weight written two ways. It does not weigh you, judge your weight or work out a medicine dose.

The Formula

One pound has been defined as exactly 0.45359237 kg since 1959, when the national standards laboratories of the United States and other English-speaking countries agreed on a shared pound¹. The current NIST handbook still lists it as exact².

Kilograms = pounds x 0.45359237

Pounds and ounces: Kilograms = (pounds + ounces / 16) x 0.45359237

How This Calculator Computes Your Result

Enter pounds as a whole number or a decimal, or switch to pounds and ounces. The tool multiplies by 0.45359237 and rounds only once, at the end. You can show kilograms to 1 or 2 decimal places. Results under 1 kg always show 2 decimals, and grams are shown too. If the ounces box is 16 or more, it rolls into pounds, so 5 lb 18 oz becomes 6 lb 2 oz.

What Your Result Means

The result is your weight in kilograms. Use this table to check a number quickly. All values were computed from the exact factor.

A quick sanity check: the kilogram number should be a little less than half the pounds number. If 150 lb gives 75 kg, something went wrong.

Lbs to Kg Chart: 90 to 269 Lbs

Every pound from 90 to 269, in kilograms to 2 decimal places.

Why Medical Forms Ask for Kilograms

Doses for many medicines, especially for children, are worked out from body weight in kilograms. A pounds and kilograms mix-up can therefore change a dose. In one case, a triage nurse typed a 17-month-old's 25 lb as 25 kg. The true weight was about 11.3 kg, so the antibiotic dose was roughly double what was intended³. The child recovered, and the mistake was caught when the mother read the discharge papers³.

This is not rare. In 1,291 weight-related medication error reports in Pennsylvania (December 2008 to November 2015), 300 involved confusion between pounds and kilograms, or 23.2 percent⁴. The authors recommend measuring, recording and passing on weight in metric units only⁴. In practice, give the unit out loud when you tell a clinic your weight, and check the weight on any form.

Treat this converter as a way to check your own numbers. It is not a substitute for a prescriber's dose, and it does not calculate one.

BMI and Sport Use Kilograms Too

BMI is defined as weight in kilograms divided by height in meters squared. The US version uses pounds and inches and multiplies by 703⁵. That 703 is the pound-to-kilogram and inch-to-meter conversions rolled into one number.

Powerlifting weigh-ins are in kilograms, on scales that show two decimals⁶. This is why the 2-decimal setting matters. 183 lb is 83.01 kg, which is over a limit of 83.0 kg even though it rounds to 83.0 at 1 decimal.

The 0.45 Shortcut and Rounding

Many people multiply by 0.45. That factor is 0.79 percent too low, and the error grows with weight. 150 lb gives 67.5 kg instead of 68.04 kg, about 0.5 kg short. At 400 lb the gap is 1.44 kg. Dividing by 2.2 errs the other way, giving 68.18 kg for 150 lb. For forms and sport, use the full factor and round only the last step.