Use this pregnancy weight gain calculator to find recommended total weight gain and weekly targets according to Institute of Medicine (IOM) clinical guidelines.
How to use this calculator
Select your unit system (metric or imperial).
Enter your pre-pregnancy height and pre-pregnancy weight.
Enter your current pregnancy week (1 to 40).
Select single baby or twin pregnancy to view recommended total gain and current target weight range.
Formula & method
IOM 2009 Pregnancy Weight Gain Guidelines
Total Target Gain = Range(Pre-Pregnancy BMI Category, Twin Status)
Normal BMI (18.5–24.9): 11.5–16 kg (25–35 lbs). Underweight: 12.5–18 kg. Overweight: 7–11.5 kg. Obese: 5–9 kg.
Example
Pre-pregnancy weight 65 kg at 170 cm (BMI 22.5, Normal): Total target 11.5–16.0 kg. At week 20: recommended gain ~3.0–5.5 kg.
Key insights
Recommended weight gain depends heavily on pre-pregnancy Body Mass Index (BMI).
During the first trimester (weeks 1–13), total weight gain is minimal (typically 0.5–2 kg / 1–4 lbs).
In the second and third trimesters, healthy weight gain averages 0.35–0.5 kg (0.8–1 lb) per week for normal BMI.
Weight gain consists of the baby, placenta, amniotic fluid, increased blood volume, uterine tissue, and body fat stores.
How to interpret your result
Recommended Total Weight Gain
The healthy overall weight gain range over the entire 40-week pregnancy based on Institute of Medicine guidelines.
Target Weight at Current Week
The expected total weight (pre-pregnancy weight plus healthy gain to date) for your current week.
Frequently asked questions
Why is pre-pregnancy BMI important?
Women with a lower pre-pregnancy BMI need to gain more weight for healthy fetal development, while women with higher BMIs require less extra weight.
Is losing weight during pregnancy safe?
Losing weight during pregnancy is generally not recommended unless specifically managed by an obstetrician.
Related calculators
Pregnancy Calculator — Estimate your due date, current gestational age and trimester progress.
BMI Calculator — Compute your Body Mass Index and see where you stand, in metric or imperial units.
Calorie Calculator — Estimate your daily calorie needs (BMR & TDEE) for maintenance, loss or gain.