Pre-Pregnancy BMI & Weight Gain Calculator
Calculate your pre-pregnancy BMI and see the recommended weight gain range during pregnancy based on IOM guidelines.
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BMI & Recommended Gain
Pre-pregnancy BMI helps determine the recommended weight gain during pregnancy.
When using pounds and inches:
BMI = (Weight in lbs / Height in inches²) × 703
When using kilograms and centimeters:
BMI = Weight in kg / (Height in m)²
IOM Recommended Weight Gain During Pregnancy (singleton):
| Pre-Pregnancy BMI | Category | Recommended Gain |
|---|---|---|
| Below 18.5 | Underweight | 28–40 lbs (12.5–18 kg) |
| 18.5–24.9 | Normal weight | 25–35 lbs (11.5–16 kg) |
| 25.0–29.9 | Overweight | 15–25 lbs (7–11.5 kg) |
| 30.0+ | Obese | 11–20 lbs (5–9 kg) |
For twins, add approximately 10–15 lbs to each range.
Weight gain by trimester:
- First trimester: 1–5 lbs total
- Second trimester: ~1 lb per week
- Third trimester: ~1 lb per week
This tool provides general guidance. Always consult your healthcare provider for personalized advice.