Pregnancy Weight Gain Calculator
Calculate recommended pregnancy weight gain based on pre-pregnancy BMI and track expected gain by trimester.
Results
Visualization
How It Works
The IOM (Institute of Medicine) recommends weight gain ranges based on pre-pregnancy BMI. Healthy weight gain supports baby development while reducing pregnancy complications.
The Formula
BMI = (Weight in lbs / Height in inches2) × 703
Expected Gain = First Trimester (~1-4 lbs) + Weekly Rate × Remaining Weeks
Variables
- BMI — Body Mass Index — weight relative to height
- IOM — Institute of Medicine — sets the guidelines for pregnancy weight gain
Worked Example
5'5", 140 lbs = BMI 23.3 (Normal). Recommended gain: 25-35 lbs. By week 20: ~11 lbs.
Practical Tips
- Most weight gain occurs in the 2nd and 3rd trimesters.
- First trimester: expect only 1-4 lbs total (morning sickness may limit gain).
- Gaining too little or too much both carry risks — aim for the recommended range.
- Twin pregnancies require significantly more weight gain.
- Focus on nutrient quality, not just calorie quantity.