Pregnancy Weight Gain Calculator
Estimate healthy pregnancy weight gain based on your pre-pregnancy BMI and current stage of pregnancy. Track recommended weight gain ranges with this free calculator.
Reviewed
August 2026
Medical Disclaimer: Results are general estimates based on population formulas and do not constitute medical advice or personalized nutrition plans. Always consult a physician or registered dietitian before making significant changes to your diet or exercise routine. Read our full Medical Disclaimer.
How This Is Calculated
Step 1: Determine Your Pre-Pregnancy BMI Category
We calculate your BMI from your pre-pregnancy height and weight, then place it into one of four categories: underweight, normal weight, overweight, or obesity.
Step 2: Apply the Recommended Gain Range for Your Category
Underweight (BMI below 18.5): 28–40 lb (12.5–18 kg) total. Normal weight (BMI 18.5–24.9): 25–35 lb (11.5–16 kg). Overweight (BMI 25–29.9): 15–25 lb (7–11.5 kg). Obesity (BMI 30 and above): 11–20 lb (5–9 kg).
Step 3: Track Weekly Gain in the 2nd and 3rd Trimester
Most weight gain happens after the first trimester. We apply a steady weekly gain rate for your BMI category to estimate your expected progress at your current week, assuming a singleton pregnancy.
Every pregnancy is different.
These ranges are general guidance for a singleton pregnancy. Your OB-GYN or midwife may recommend a different target based on your health history, multiples, or pre-existing conditions.
Sources
Weight Gain During Pregnancy — American College of Obstetricians and Gynecologists (ACOG), 2013
Weight Gain During Pregnancy: Reexamining the Guidelines — Institute of Medicine & National Research Council, 2009
Frequently asked questions
How much weight should I gain during pregnancy?
It depends on your pre-pregnancy BMI. Most guidelines recommend 25–35 lb for a normal BMI, with higher ranges for underweight and lower ranges for overweight or obese pre-pregnancy BMI.
Is this calculator accurate for twin pregnancies?
No — this calculator is designed for singleton pregnancies. Twin and multiple pregnancies have separate, higher recommended weight gain ranges.
What if I'm gaining weight faster or slower than recommended?
Some variation week to week is normal. If your gain is consistently far outside the recommended range, talk to your OB-GYN or midwife about your individual plan.
Does this calculator account for the first trimester?
Yes — first trimester gain is typically small (1–4.5 lb total), with most of the recommended gain occurring during the 2nd and 3rd trimesters.