The average weight of a 2-year-old girl is 26.5 pounds, while the average weight of a 2-year-old boy is 27.5 pounds. A child's height varies alongside his body weight, so it is important to find both measurements to calculate a healthy weight using the body mass index.
BMI is a measurement of body fat percentage. To calculate one's BMI, his weight in kilograms must be divided by the square of his height in meters. If using American measurements, ounces and fractions must be converted to decimal values. Then, the weight in pounds is divided by the squared height in inches, and this number is multiplied by 703. Children's BMI calculators differ slightly from those for adults. Age and sex is taken into consideration, as body fat differs between female and male children.