Health & Fitness
Pregnancy Weight Gain Calculator (IOM Guidelines)
See your trimester-by-trimester healthy weight-gain range based on pre-pregnancy BMI. Backed by Institute of Medicine guidelines.
Pregnancy type
lb
in
Pre-pregnancy BMI
23.3
normal
Total healthy gain
25–35 lb
IOM/NASEM 2009 guidelines
Expected by week 20
7.3–12.3 lb
Healthy range vs your week
0 lb71240 lb
Trajectory
Recommended weight gain by week
Cumulative gain (lb)
Lower healthy boundUpper healthy bound
How this is calculated
The Institute of Medicine (now NASEM) publishes the standard pregnancy weight-gain ranges, calibrated by pre-pregnancy BMI:
- BMI < 18.5 (underweight): 28–40 lb total gain
- BMI 18.5–24.9 (normal): 25–35 lb
- BMI 25–29.9 (overweight): 15–25 lb
- BMI ≥ 30 (obese): 11–20 lb
We allocate 1.1–4.4 lb to the first trimester, then distribute the remainder evenly across weeks 14–40. Twin pregnancies use the higher IOM ranges (37–54 lb for normal-weight).
Always work with your prenatal provider — these ranges are population-level, not individual prescriptions.
Frequently asked
- We use the 2009 IOM (now NASEM) recommendations — still the standard reference cited by the CDC and ACOG.
- Twin pregnancies have separate IOM ranges (37–54 lb for normal-weight). Toggle the multiples option to apply them.