Each stone is 14 lb. To calculate the number of stones in 120 kg, we divide 120 kg by 14 lb/stone. 120 kg / 14 lb/stone = 8.57 st. Since there are whole numbers only, we multiply the decimal portion (.57) by 14 lb to get the number of pounds. .57 x 14 lb = 8 lb. Therefore, 120 kg is equal to 18 st 8 lb.