Pregnancy Weight Gain Calculator
See a healthy pregnancy weight gain range, total and by week, based on pre-pregnancy BMI.
About the Pregnancy Weight Gain Calculator
The US Institute of Medicine (now National Academy of Medicine) 2009 guidelines, endorsed by ACOG and CDC, set total gain by pre-pregnancy BMI: 28–40 lb if underweight, 25–35 lb at a healthy weight, 15–25 lb if overweight and 11–20 lb with obesity. Most gain happens after the first trimester, when 1.1–4.4 lb is typical.
The formula
Target = range for BMI category; weekly ≈ rate × (weeks − 13) + first-trimester gain
Worked example
Example: Recommended total gain = 28 lb – 40 lb
- Inputs: Units: lb / in; Pre-pregnancy weight: 170 kg or lb; Height: 81 cm or in; Current week: 30 weeks; Carrying: One baby.
- Formula: Target = range for BMI category; weekly ≈ rate × (weeks − 13) + first-trimester gain
- Result: Recommended total gain = 28 lb – 40 lb
Questions people ask
Is it bad to gain less?
Too little gain is linked to small babies; talk to your provider.
Do I need extra calories?
None in the first trimester, about 340 kcal/day in the second and 450 in the third (for a healthy-weight person).