Pregnancy Weight Gain Calculator

Calculate recommended weight gain during pregnancy based on your pre-pregnancy BMI and current week, following IOM guidelines.

Results

Visualization

How It Works

The Institute of Medicine (IOM) provides weight gain recommendations based on pre-pregnancy BMI. Gaining too little or too much can affect outcomes. Always discuss with your provider. Not medical advice.

The Formula

First trimester: ~1-4.4 lbs total
After that: 0.4-1.3 lbs/week depending on BMI category

Variables

  • BMI — Body Mass Index = (weight_lbs / height_in^2) x 703
  • IOM ranges — Underweight: 28-40 lbs, Normal: 25-35, Overweight: 15-25, Obese: 11-20

Example

140 lbs, 5'4" (BMI 24.0, normal weight), 20 weeks pregnant: recommended gain is about 10-11 lbs so far.

Tips

  • Weight gain is not linear -- most occurs in the second and third trimesters
  • Twin pregnancies have higher recommended ranges (37-54 lbs for normal BMI)
  • Focus on nutrient quality, not just quantity
  • Consult your healthcare provider for personalized guidance

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