Pregnancy Weight Gain Calculator – IOM Guidelines
Free pregnancy weight gain calculator: enter your pre-pregnancy weight, height and weeks pregnant to get your BMI category and recommended weight gain range. Based on IOM 2009 guidelines. No sign-up, runs in your browser.
Pregnancy Weight Gain Calculator
Enter your pre-pregnancy weight, height and current weeks pregnant for IOM-based recommended gain.
How the pregnancy weight gain calculator works
The calculator uses your pre-pregnancy weight and height to compute BMI, then applies the IOM 2009 ranges: Underweight 12.5–18 kg, Normal 11.5–16 kg, Overweight 7–11.5 kg, Obese 5–9 kg. Results are shown in both kg and lb.
Understanding pregnancy weight gain
Gaining weight during pregnancy is normal and necessary. The weight supports your baby's growth, the placenta, amniotic fluid, increased blood volume, and stored fat for breastfeeding. The Institute of Medicine (IOM) 2009 guidelines provide evidence-based ranges to help reduce risks such as gestational diabetes, cesarean delivery, and postpartum weight retention while supporting healthy fetal development.
Your pre-pregnancy BMI determines your category. Underweight women need to gain more to support the baby and avoid low birth weight. Overweight and obese women are advised to gain less to reduce pregnancy complications. The calculator gives you a range; aim for the middle of the range when possible, but always follow your healthcare provider's advice.
Weight gain is not linear. Many women gain little in the first trimester, especially if they have nausea. The second and third trimesters typically see steady gain. Use our BMI calculator to check your pre-pregnancy BMI, and our calorie calculator to estimate your energy needs during pregnancy. This tool is for guidance only; your provider may adjust recommendations based on your individual situation.