Hi.My baby girl age is 1 year and 2 months she weighed 12.40 kg.Her birth weight was 4.25 kg.Is she gained the correct weight or not.How would we calculate the weight? I mean based on birth weight or average weight of the child of this age?

A. Hello mommy, How and When to measure weight of the Infant Weigh the baby at birth at one week and then after 10 days. ... While there is no set formula but weighing the baby once a month up to one year should be sufficient unless there is a reason to weigh them more frequently. By one year, the average weight of a baby girl is approximately 19 pounds 10 ounces (8.9 kg), with boys weighing about 21 pounds 3 ounces (9.6 kg). your babys weight is absolutely fine.