Pregnancy Weight Gain Calculator
Calculate recommended pregnancy weight gain based on pre-pregnancy BMI.
The Formula
Underweight (<18.5): 28–40 lbs
Normal (18.5–24.9): 25–35 lbs
Overweight (25–29.9): 15–25 lbs
Obese (≥30): 11–20 lbs
BMI = 65 / (1.65)² = 23.9 (Normal)
Recommended gain: 25–35 lbs (11–16 kg)
Target range: 76–81 kg at delivery
How Much Weight Should You Gain During Pregnancy?
The Institute of Medicine (IOM) — now the National Academy of Medicine — provides the most widely used pregnancy weight gain recommendations, based on your pre-pregnancy BMI. For a single pregnancy: underweight women (BMI under 18.5) should gain 28–40 pounds; normal weight women (BMI 18.5–24.9) should gain 25–35 pounds; overweight women (BMI 25–29.9) should gain 15–25 pounds; obese women (BMI 30 or higher) should gain 11–20 pounds. For twins, the recommended ranges are approximately 10 pounds higher across all categories.
Where Does the Weight Actually Go?
Pregnancy weight gain is not all fat storage. A typical breakdown for a woman gaining 30 pounds: the baby accounts for about 7–8 pounds, the placenta 1–2 pounds, amniotic fluid 2 pounds, uterus growth 2 pounds, breast tissue 1–2 pounds, blood volume increase 3–4 pounds, body fluids 3–4 pounds, and maternal fat stores 6–8 pounds. This is why healthy weight gain is not only normal but necessary — it directly supports fetal development and prepares the body for labor and breastfeeding.
Trimester-by-Trimester Weight Gain Pattern
Most weight gain happens in the second and third trimesters. In the first trimester, minimal weight gain is expected — typically 1–4 pounds total, or even slight weight loss if nausea is significant. Starting in the second trimester, most women with a normal pre-pregnancy BMI gain approximately 1 pound per week. Your provider will track weight gain at each prenatal visit and can advise if you are gaining too quickly or too slowly for your specific situation.
Frequently Asked Questions
When do most women gain weight during pregnancy?
The majority of weight gain happens in the second and third trimesters. First trimester weight gain is minimal — 1–4 pounds is typical, and some women lose weight early due to nausea and food aversions. Starting around weeks 13–16, weight gain picks up to roughly 1 pound per week for normal-weight women through the third trimester.
What happens if you gain too much weight during pregnancy?
Excessive pregnancy weight gain is associated with increased risks of gestational diabetes, high blood pressure and preeclampsia, a larger baby (macrosomia), higher rates of cesarean delivery, and postpartum weight retention. It can also increase the child's risk of childhood obesity. Your prenatal provider monitors weight gain at each visit precisely because staying within recommended ranges benefits both mother and baby.
What if I am not gaining enough weight during pregnancy?
Inadequate weight gain is also a concern — it can be associated with preterm birth and low birth weight. If you are struggling to gain enough due to nausea, food aversions, or morning sickness, focus on calorie-dense nutrient-rich foods and talk to your provider. Severe nausea (hyperemesis gravidarum) affecting weight gain warrants medical evaluation.
Can I diet or restrict calories during pregnancy?
Active calorie restriction is not recommended during pregnancy, including for women who are overweight. The focus should be on eating nutrient-dense whole foods rather than restricting calories. Some overweight or obese women may gain little or no net weight while still providing adequate nutrition for the baby. Always discuss weight management goals during pregnancy with your OB or midwife.
How much weight is safe to lose after giving birth?
Most women lose 10–15 pounds immediately after delivery (baby, placenta, amniotic fluid, and blood). The remaining pregnancy weight typically comes off gradually over 6–12 months postpartum. Breastfeeding can support postpartum weight loss. Moderate exercise cleared by your provider and a balanced diet — rather than aggressive restriction — is the safest approach, especially while nursing.