Pregnancy Weight Gain Calculator

The Institute of Medicine (IOM) recommends total pregnancy weight gain ranges based on pre-pregnancy BMI category: 12.5-18 kg for underweight, 11.5-16 kg for normal weight, 7-11.5 kg for overweight, and 5-9 kg for obese. These ranges reflect that starting from a higher pre-pregnancy weight generally calls for less additional gain, since existing energy reserves are already greater.

If you enter your current week, this calculator estimates a recommended gain-to-date by applying a small, roughly consistent first-trimester gain (about 0.5-2 kg, regardless of BMI category, following common guidance) and then spreading the remainder of your recommended total gain evenly across the following weeks. This is a simplified linear approximation, actual recommended gain per week can vary somewhat by trimester and individual circumstances, so use it as a general guide rather than an exact target.

For example, a pre-pregnancy height of 165 cm and weight of 62 kg gives a BMI of about 22.8, in the Normal Weight category, so the recommended total gain range is 11.5 to 16 kg. At week 20, the estimated recommended gain-to-date falls between about 3.4 and 5.6 kg.