Pregnancy Weight Gain Calculator

Gaining the right amount of weight during pregnancy helps ensure your baby grows well while keeping you healthy. Too little can lead to low birth weight; too much increases the risk of gestational diabetes, preeclampsia, and a difficult delivery.

The IOM guidelines offer evidence-based targets that balance fetal growth with maternal health. They account for the fact that women who start at different weights have different metabolic needs during pregnancy.

Your pre-pregnancy BMI determines your recommended weight gain range. The IOM (Institute of Medicine) published updated guidelines in 2009 that most doctors worldwide follow. Note: these are general guidelines — your doctor may recommend different targets based on your specific health situation.

BMI is calculated as your weight in kilograms divided by the square of your height in metres. For example, a woman who weighs 58 kg and is 162 cm tall has a BMI of 22.1, placing her in the normal weight category.

First trimester (weeks 1–13): Most women gain only 0.5–2 kg. Nausea may actually cause some weight loss initially. The baby is still very small, so most gain comes from increased blood volume and breast tissue.

Second trimester (weeks 14–27): This is when steady, consistent gain begins. For a normal-weight woman, this means roughly 0.42 kg per week. The baby is growing rapidly, and so is the placenta and amniotic fluid.

Third trimester (weeks 28–40): Growth continues at a similar rate. The baby puts on most of its fat stores during this period. You may notice your appetite increasing significantly.