Pregnancy Weight Gain Calculator

Tracking weight gain week by week, measured against your pre-pregnancy Body Mass Index (BMI), gives a clearer read on a pregnancy than a single end-of-term total. The tool maps recommended gain across each week in line with current 2026 guidance, supporting healthy development for the baby and steady well-being for the mother.

The recommendations come from the Institute of Medicine (IOM) guidelines, which set different target ranges depending on whether pre-pregnancy BMI falls in the underweight, normal weight, overweight, or obese category. That total is then spread across the trimesters, with little expected in the first and a steadier weekly pace through the second and third, on the assumption of a singleton pregnancy.

These figures are guidelines rather than rules, and what is right for you can differ, so your healthcare provider remains the best source for advice tailored to your pregnancy. Watching only the final total while ignoring the weekly trajectory tends to breed either needless worry or unhealthy shortcuts, when the gradual progression is what the guidance is really about.