Convert Pound to Kilogram

One pound is defined as exactly 0.45359237 kilograms — a figure set by international agreement in 1959 and unchanged since. The practical upshot is that any pound-to-kilogram conversion is mathematically exact; accumulated error comes only from rounding the final display, not from an approximate factor.

Body weight is the most common trigger. A doctor's office in the US records weight in pounds; a hospital abroad may record it in kilograms. At 150 lb, a patient weighs 68.0389 kg — usually rounded to 68 kg. Drug dosing is sometimes calculated per kilogram of body weight, so a precise conversion matters more than it might seem from a casual weighing.

Shipping and freight flip the context. A 100 lb package sits just under the 45.36 kg mark. Many international carriers quote surcharges by the kilogram, so knowing the exact metric equivalent lets you compare rates without surprise overages. For heavy machinery, where specifications might list component weights in either system, the defined factor ensures no rounding creep over repeated calculations.

A gotcha worth noting: the avoirdupois pound used for everyday weight is the same in both the US and the UK (0.45359237 kg), but the UK stone — 14 pounds — has no US equivalent. When someone quotes a UK body weight as '11 stone 4,' that is 158 lb or 71.67 kg, not a number you can convert directly without first resolving the stone.