Pregnancy Weight Gain Calculator

Gaining weight in pregnancy is healthy and expected — it supports your baby's growth, the placenta, extra blood and fluid, and stores for breastfeeding. The right amount depends on where your weight started, which is why the recommendation is tied to your pre-pregnancy BMI.

This calculator applies the Institute of Medicine's guidelines: the range shown is the recommended total gain across a single pregnancy for your starting category. People who began underweight are advised to gain more; those who began overweight or obese, less.

It's a population guideline, not a personal prescription. How gain is distributed across the trimesters, and what's right for you specifically, are things your healthcare provider will tailor to your health, your baby's growth, and any complications.

Method. We calculate your pre-pregnancy BMI from your height and pre-pregnancy weight, then look up the Institute of Medicine's recommended total gain for that BMI category: underweight 12.5–18 kg, normal 11.5–16 kg, overweight 7–11.5 kg, and obese 5–9 kg. The range is shown in your preferred weight unit.

Cutoffs. These use the standard BMI categories (not the Asian-adjusted set), matching how the IOM guidelines are defined.

Confidence. We label this moderate confidence: it's an evidence-based guideline for single pregnancies, but individual advice — including for twins or specific health conditions — should come from your provider.