Pregnancy Weight Gain Calculator
Track recommended pregnancy weight gain by current pregnancy week and pre-pregnancy BMI. Total ranges are set by the Institute of Medicine (IOM).
Current Progress (optional)
How to use the Pregnancy Weight Gain Calculator
- Enter your inputs into the Pregnancy Weight Gain Calculator above.
- Results update instantly as you type — no submit button needed.
- Adjust any value to see how the result changes in real time.
IOM weight gain guidelines
Underweight (BMI <18.5): 28–40 lb · · · Normal (18.5–24.9): 25–35 lb · · · Overweight (25–29.9): 15–25 lb · · · Obese (30+): 11–20 lb
After the first trimester (~3–5 lb total), weight gain should be roughly 1 lb/week for normal-weight women, less for overweight or obese pre-pregnancy BMIs.
Worked example
A pre-pregnancy normal-BMI woman at 20 weeks: expected weight gain so far ≈ 5 lb (first trimester) + 1 lb/week × 7 weeks (week 13–20) ≈ 12 lb. By full term (40 weeks): 25–35 lb total.
Frequently asked questions
What happens if I gain too much?
Excessive gain raises risks of gestational diabetes, hypertension, larger-than-average babies, complicated delivery and more difficulty losing weight postpartum.
What if I'm carrying twins?
IOM guidelines for twins: 37–54 lb (normal BMI), 31–50 lb (overweight), 25–42 lb (obese). Triple gain for triplets is roughly proportional.
Is weight gain only baby weight?
Roughly: baby 7–8 lb, placenta 1.5 lb, amniotic fluid 2 lb, uterus growth 2 lb, breast tissue 2 lb, blood volume 4 lb, additional fluid retention 4 lb, fat stores 6–8 lb. Total ≈ 25–35 lb for a singleton.