Pregnancy Weight Gain Calculator
Track your pregnancy weight gain week by week. This calculator uses IOM guidelines to determine if your weight gain is on track based on your pre-pregnancy BMI.
How Much Weight Should I Gain?
Healthy weight gain during pregnancy depends largely on your Pre-Pregnancy Body Mass Index (BMI). The Institute of Medicine (IOM) provides specific guidelines to ensure the health of both you and your baby.
This Pregnancy Weight Gain Calculator uses these official 2009 guidelines to compare your current progress against the recommended range for your specific week of pregnancy.
Weight Gain Guidelines (Singleton Pregnancy)
- Underweight (BMI < 18.5): 28-40 lbs (12.5-18 kg)
- Normal Weight (BMI 18.5-24.9): 25-35 lbs (11.5-16 kg)
- Overweight (BMI 25-29.9): 15-25 lbs (7-11.5 kg)
- Obese (BMI ≥ 30): 11-20 lbs (5-9 kg)
Where does the weight go?
It is not just fat! Here is a rough breakdown of where that 30 lbs typically goes:
- Baby: ~7.5 lbs
- Placenta: ~1.5 lbs
- Amniotic Fluid: ~2 lbs
- Uterus Growth: ~2 lbs
- Breast Tissue: ~2 lbs
- Blood Volume: ~4 lbs
- Fluids: ~4 lbs
- Fat Stores (for breastfeeding): ~7 lbs
Gaining too little can increase the risk of a low birth weight infant, while gaining too much can lead to complications like gestational diabetes, pre-eclampsia, and difficulty losing weight postpartum. Always consult your doctor for personalized advice.
If you are curious about your conception date or due date, try our Due Date Calculator or Conception Date Calculator.
? Frequently Asked Questions
Most women gain very little (1-4 lbs) in the first trimester (weeks 0-13) due to morning sickness or food aversions. Steady weight gain usually begins in the second trimester.
Sudden rapid weight gain can be a sign of fluid retention or pre-eclampsia, but gradual increase above the curve might just mean you need to adjust your caloric intake. Speak with your healthcare provider.
We have a specific 'Carrying Twins' toggle! The IOM recommends higher ranges for twin pregnancies: Normal BMI (37-54 lbs), Overweight (31-50 lbs), and Obese (25-42 lbs).
Dieting to lose weight is generally not recommended during pregnancy unless specifically supervised by a doctor for obese patients, as it can deprive the growing baby of nutrients.