Pregnancy Weight Gain Calculator
Find your recommended pregnancy weight gain range based on your pre-pregnancy BMI, following guidelines from the American College of Obstetricians and Gynecologists (ACOG) and the Institute of Medicine (IOM). Always consult your healthcare provider for personalized advice.
Your Information
Pre-Pregnancy BMI
Recommended Total Gain
Gain So Far
Week-by-Week Recommended Gain
Based on ACOG/IOM guidance — most weight gain occurs in the 2nd and 3rd trimesters.
| Trimester / Period | Weeks | Weekly Rate |
|---|
ACOG / IOM Pregnancy Weight Gain Guidelines
The recommended amount of weight to gain during pregnancy depends primarily on your pre-pregnancy BMI. Here is the summary for a single (singleton) pregnancy:
| Pre-Pregnancy BMI | BMI Category | Total Gain (lbs) | 2nd & 3rd Tri/week |
|---|---|---|---|
| Under 18.5 | Underweight | 28–40 lbs | 1–1.3 lbs/wk |
| 18.5–24.9 | Normal weight | 25–35 lbs | 0.8–1 lb/wk |
| 25.0–29.9 | Overweight | 15–25 lbs | 0.5–0.7 lbs/wk |
| 30.0+ | Obese | 11–20 lbs | 0.4–0.6 lbs/wk |
For twin pregnancies, recommended total gain is higher — typically 37–54 lbs for normal-weight individuals, 31–50 lbs for overweight, and 25–42 lbs for those with obesity.
Where Does the Weight Go?
Weight gained during pregnancy is not just body fat. For a normal-weight person gaining about 30 lbs, the approximate breakdown is:
- Baby: ~7.5 lbs
- Placenta: ~1.5 lbs
- Amniotic fluid: ~2 lbs
- Uterus growth: ~2 lbs
- Breast tissue: ~2 lbs
- Blood volume increase: ~4 lbs
- Body fluids/water: ~4 lbs
- Maternal fat stores: ~7 lbs
Frequently Asked Questions
What if I gain more or less than recommended?
Gaining too little during pregnancy is associated with preterm birth and low birth weight. Gaining too much is linked with gestational diabetes, cesarean delivery, and postpartum weight retention. Neither is automatically cause for alarm — your healthcare provider can assess your specific situation.
Is weight gain in the first trimester normal?
Most guidelines recommend only 1–4 lbs of total weight gain in the first trimester (weeks 1–12). Many women gain very little or even lose weight in the first trimester due to nausea. The majority of pregnancy weight gain occurs in the second and third trimesters.
How do I calculate my pre-pregnancy BMI?
BMI = weight (kg) ÷ height² (m²), or in imperial units: BMI = (weight in lbs × 703) ÷ height² (inches²). You can also use our BMI calculator for a quick conversion.
