Pregnancy Weight Gain Calculator
Get personalized weight gain recommendations based on your pre-pregnancy BMI.
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
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Request a ToolHow to Use the Pregnancy Weight Gain Calculator
This calculator provides personalized weight gain recommendations based on Institute of Medicine (IOM) guidelines and your pre-pregnancy BMI. Here is how to use it:
- Select your units. Choose pounds and inches or kilograms and centimeters.
- Enter your pre-pregnancy weight and height. Use your weight before becoming pregnant, not your current weight. Height is used to calculate BMI.
- Enter your current gestational week. This allows the calculator to estimate how much you should have gained so far.
- Read your results. The calculator shows your pre-pregnancy BMI category, the recommended total weight gain range, the recommended weekly rate during the second and third trimesters, and an estimate of expected gain at your current week.
About the Pregnancy Weight Gain Calculator
The IOM guidelines (updated 2009) provide weight gain recommendations based on pre-pregnancy BMI: underweight women (BMI below 18.5) should gain 28-40 lbs, normal weight women (BMI 18.5-24.9) should gain 25-35 lbs, overweight women (BMI 25-29.9) should gain 15-25 lbs, and obese women (BMI 30+) should gain 11-20 lbs. These are total recommendations for a singleton pregnancy.
Weight gain in the first trimester is typically small, around 1-4.5 pounds total. Most weight gain occurs in the second and third trimesters at a steady weekly rate. These numbers are guidelines, not strict targets. Individual circumstances vary, and your healthcare provider is the best source for personalized advice.
Frequently Asked Questions
What are the IOM pregnancy weight gain guidelines?
The 2009 Institute of Medicine guidelines recommend: 28-40 lbs for underweight women (BMI below 18.5), 25-35 lbs for normal weight women (BMI 18.5-24.9), 15-25 lbs for overweight women (BMI 25-29.9), and 11-20 lbs for obese women (BMI 30+). For twin pregnancies, the recommendations are higher and vary by starting BMI.
What happens if I gain too much or too little weight during pregnancy?
Gaining too much weight increases risk of gestational diabetes, preeclampsia, cesarean delivery, and having a large baby. Gaining too little is associated with preterm birth, low birth weight, and nutrient deficiencies. Both extremes are associated with obesity risk in the child. If your weight gain is outside the recommended range, speak with your healthcare provider about adjusting diet and physical activity.
Where does pregnancy weight gain actually go?
For a woman gaining 30 pounds total, approximately 7-8 lbs is the baby, 1.5 lbs is the placenta, 2 lbs is the amniotic fluid, 2 lbs is uterus growth, 1-2 lbs is breast tissue, 3-4 lbs is blood volume increase, 2 lbs is body fluids, and 6-8 lbs is fat stores needed for breastfeeding. Most of this weight is lost in the weeks and months after delivery.
How much weight is normal to gain in the first trimester?
During the first trimester (weeks 1-12), total weight gain is typically 1-4.5 pounds. Some women lose weight due to morning sickness. The baby is only about 1 inch long at 8 weeks, so fetal growth is not the main factor. Most first-trimester weight gain is from increased blood volume and uterine growth. Rapid weight gain in the first trimester can indicate excess calorie intake rather than fetal development.