A mass of 57 kilograms is equivalent to approximately 125.66 pounds. It is also equivalent to 8 stones and 13.66 pounds. Kilograms measure an object's mass, whereas stones and pounds measure an object's weight.
According to Metric Conversions, a stone is equivalent to 14 pounds. In addition, 1 kilogram is equal to approximately 2.2046 pounds. Therefore, 57 kilograms is equivalent to 57 x 2.2046 = 125.66 pounds. Dividing 125.66 by 14 and taking the remainder gives the number of stones and pounds. Since 8 stones equal 112 pounds, this leaves 13.66 pounds as a remainder. According to Unit Conversion, the stone is used in the British Isles to express human body weight and is part of the British Isles' Imperial system of weights and measures. It was historically used to measure agricultural commodities.