Free Pregnancy Tool
Weekly Pregnancy Weight Gain
Enter your height, your weight before pregnancy and your current week. We show the Institute of Medicine (IOM, 2009) range for your BMI.
General information only, not medical advice. Ask your doctor or midwife.
How this works
Formula: BMI = weight (kg) ÷ height (m)². IOM 2009 total gain: 28–40 lb (BMI < 18.5), 25–35 lb (18.5–24.9), 15–25 lb (25–29.9), 11–20 lb (30+).
- Your pre-pregnancy BMI puts you in one of four groups.
- For one baby, the IOM expects about 1.1 to 4.4 lb (0.5 to 2 kg) in the first trimester, then a steady weekly gain: 1 to 1.3 lb, 0.8 to 1 lb, 0.5 to 0.7 lb or 0.4 to 0.6 lb a week, depending on your group.
- For twins, the IOM gives total ranges only: 37–54 lb, 31–50 lb and 25–42 lb for the healthy, overweight and obese groups. It set no range for the underweight group. The weekly line for twins is a simple straight-line guide to the total by week 37.
- If you add your current weight, we show where you are against the range for your week.
Everything is worked out in your browser. Belly Weekly does not send or store your answers.
Questions
What if I'm above or below the range?
Ranges are a guide, not a test you pass or fail. Talk to your doctor or midwife; they know your whole picture.
Should I diet during pregnancy?
Do not start a diet to lose weight in pregnancy unless your doctor advises it.
Why does BMI before pregnancy matter?
The IOM ranges are based on pre-pregnancy BMI, so use your weight from before you were pregnant.