Pregnancy Weight Gain Calculator
See your recommended weight gain range based on pre-pregnancy BMI, with trimester targets and a week-by-week projection. Based on IOM/ACOG clinical guidelines.
The Institute of Medicine (IOM) and American College of Obstetricians and Gynecologists (ACOG) publish weight gain guidelines based on pre-pregnancy BMI. Gaining within the recommended range is associated with the best outcomes for both mother and baby.
Enter Your Details
Your Pregnancy Weight Gain Plan
Trimester Breakdown
Week-by-Week Projection
| Week | Min Weight | Target Weight | Max Weight | Trimester |
|---|
How This Calculator Works
This tool implements the 2009 IOM guidelines (reaffirmed by ACOG in 2024) for gestational weight gain. Your pre-pregnancy BMI determines which weight gain category you fall into. The guidelines assume that most weight gain occurs in the second and third trimesters, with minimal gain (1-4.5 lbs) during the first trimester when the fetus is still very small.
The weekly gain rate during the second and third trimesters is approximately constant within each BMI category. For normal-weight women, the recommended rate is about 1 pound per week. For overweight women, approximately 0.6 lbs per week. For obese women, approximately 0.5 lbs per week. Underweight women should aim for approximately 1.1 lbs per week during this period.
Where Does the Weight Go?
The recommended weight gain during pregnancy is not all body fat. For a typical 30-lb total gain in a normal-weight singleton pregnancy, the approximate distribution is: baby (7.5 lbs), placenta (1.5 lbs), amniotic fluid (2 lbs), uterine growth (2 lbs), breast tissue (2 lbs), increased blood volume (4 lbs), increased body fluid (4 lbs), and maternal fat stores (7 lbs). The maternal fat stores provide energy reserves for breastfeeding and postpartum recovery.
Nutrition During Pregnancy
Calorie needs increase modestly during pregnancy. In the first trimester, no additional calories are typically needed — focus on nutrient density. In the second trimester, add approximately 340 calories per day. In the third trimester, add approximately 450 calories per day. Use our Calorie Calculator for your baseline, then add trimester-specific amounts.
Protein requirements increase to approximately 1.1g per kg of pre-pregnancy body weight (up from 0.8g/kg). Key micronutrients include folate (400-800mcg for neural tube development), iron (27mg for increased blood volume), calcium (1,000mg for fetal bone development), and DHA (200-300mg for brain development). Stay well-hydrated — water needs increase by 24-32 oz per day during pregnancy.
Exercise During Pregnancy
ACOG recommends 150 minutes of moderate-intensity aerobic activity per week during pregnancy for women without obstetric or medical complications. Moderate intensity means you can talk but not sing during the activity — roughly Zone 2-3 on the Target Heart Rate Calculator. Activities like walking, swimming, and prenatal yoga are well-studied. Track your activity with the Calories Burned Calculator. Rest and recovery are equally important — optimize your schedule with the Sleep Calculator.
Risks of Gaining Too Much or Too Little
Excessive gain increases risk of gestational diabetes, preeclampsia, cesarean delivery, macrosomia (large baby), postpartum weight retention, and childhood obesity in the offspring. Insufficient gain increases risk of preterm birth, low birth weight, and failure to thrive. Both scenarios are associated with worse maternal and neonatal outcomes than gaining within the recommended range.
If you're planning pregnancy, establish a healthy baseline with our BMI Calculator, Body Fat Calculator, and Ideal Weight Calculator. Use the Ovulation Calculator and Period Calculator for conception planning. Once pregnant, estimate your delivery date with the Due Date Calculator.
IOM Weight Gain Guidelines by Pre-Pregnancy BMI
| Pre-Pregnancy BMI | Category | Singleton (lbs) | Twins (lbs) | Weekly Rate (2nd-3rd tri) |
|---|---|---|---|---|
| < 18.5 | Underweight | 28 – 40 | 50 – 62 | ~1.0 – 1.3 lb/wk |
| 18.5 – 24.9 | Normal Weight | 25 – 35 | 37 – 54 | ~0.8 – 1.0 lb/wk |
| 25.0 – 29.9 | Overweight | 15 – 25 | 31 – 50 | ~0.5 – 0.7 lb/wk |
| ≥ 30.0 | Obese | 11 – 20 | 25 – 42 | ~0.4 – 0.6 lb/wk |
Frequently Asked Questions
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