Pregnancy Weight Gain Calculator
Get IOM-recommended weight gain targets based on your BMI and week of pregnancy.
Last updated: June 13, 2026
Calculator
Results
Single pregnancy
Normal Weight
At week 20
How to Use This Calculator
- 1Enter your pre-pregnancy weight in pounds.
- 2Enter your height in inches.
- 3Enter your current week of pregnancy.
- 4Select single or twin pregnancy.
- 5View recommended total gain, expected gain by now, and target delivery weight.
Formula Explanation
The Institute of Medicine (IOM) provides weight gain recommendations based on pre-pregnancy BMI. Underweight women should gain more, while overweight or obese women should gain less. Weight gain is minimal in the first trimester and accelerates in the second and third trimesters.
Variables:
Worked Examples
140 lbs, 5'5" (65"), week 20, single
- 1. BMI = (140 ÷ 65²) × 703 = 23.3 (Normal)
- 2. Recommended: 25-35 lbs total
- 3. Expected by week 20: ~9.4 lbs
- 4. Target delivery weight: 165-175 lbs
180 lbs, 5'4" (64"), week 30, single
- 1. BMI = (180 ÷ 64²) × 703 = 30.9 (Obese)
- 2. Recommended: 11-20 lbs total
Why Use This Calculator
- Personalized recommendations based on your BMI category.
- Shows expected weight gain for your current week.
- Includes twin pregnancy guidelines.
- Based on official IOM clinical guidelines.
Tips & Best Practices
- Weight gain is not linear — expect little gain in the first 12 weeks, then steady increase.
- Do not try to "diet" during pregnancy. Focus on nutrient-dense foods.
- Gaining too little can be just as harmful as gaining too much.
- Discuss your individual plan with your provider — these are general guidelines.
Common Mistakes to Avoid
❌ Comparing your weight gain to other pregnant women.
✅ Recommendations vary significantly by BMI category. A normal-weight woman gains 25-35 lbs while an overweight woman should gain 15-25 lbs.
❌ Trying to restrict calories to limit weight gain.
✅ Never restrict calories during pregnancy without medical supervision. Focus on nutrition quality, not calorie restriction.
Frequently Asked Questions
How much weight should I gain during pregnancy?
When does pregnancy weight gain start?
Is it normal to lose weight in the first trimester?
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<iframe src="https://redicalc.com/embed/health/pregnancy-weight-gain-calculator" width="100%" height="600" style="border:none;border-radius:12px;box-shadow:0 1px 3px rgba(0,0,0,0.1);" title="Pregnancy Weight Gain Calculator — RediCalc.com" loading="lazy" allowtransparency="true"></iframe>Disclaimer: This calculator is provided for informational and educational purposes only. Results are estimates and should not be used as a substitute for professional advice. RediCalc.com makes no guarantees regarding the accuracy, completeness, or suitability of any calculations. Always consult a qualified professional before making financial, health, construction, or other important decisions.
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