What is the formula for calculating child weight?

The formula for calculating the weight of children from one to six months is weight (kg)= birth weight +(0.6× month age), weight of children from six to twelve months (kg)= birth weight +(0.5× month age), underweight of children indicates malnutrition, and attention should be paid to supplementary nutrition at ordinary times. Overweight of children indicates overnutrition. Light diet and weight loss should be paid attention to at ordinary times.