Pregnancy BMI Calculator
Pregnancy BMI & Weight Gain
Calculate pre-pregnancy BMI and recommended weight gain
lbs
Formula
BMI = (Weight in lbs / Height in inches^2) x 703 | Recommended Gain = Based on IOM guidelines by BMI category | Expected Gain at Week X = Total Recommended x (Week / 40)
Frequently Asked Questions
How much weight should I gain during pregnancy?
The IOM recommends: Underweight (BMI <18.5): 28-40 lbs, Normal weight (BMI 18.5-24.9): 25-35 lbs, Overweight (BMI 25-29.9): 15-25 lbs, Obese (BMI 30+): 11-20 lbs. For twins, add approximately 10-15 lbs to each range.
When do you gain the most weight during pregnancy?
Most weight gain occurs during the 2nd and 3rd trimesters. In the first trimester, total gain is typically 1-4.5 lbs. After that, steady weekly gain is expected based on your pre-pregnancy BMI category.
Is BMI accurate during pregnancy?
BMI is most meaningful when calculated using your pre-pregnancy weight. During pregnancy, weight gain includes the baby, placenta, amniotic fluid, increased blood volume, and breast tissue, so current BMI isn't a useful health measure.
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