The equivalent of 171 pounds is approximately 77.727 kilograms. This same mass is also equivalent to 77,727 grams. Because a kilogram is equal to approximately 2.2 pounds, the conversion of 171 pounds to kilograms requires dividing the number of pounds by 2.2 pounds per kilogram.
The kilogram is a unit of mass in the International System of Units, a system favored by the scientific community and one that is used worldwide. This system is also commonly known as the metric system. The pound is a unit of mass in the U.S. System of customary units, a measurement system used almost exclusively in the United States.