Pregnancy Weight Gain Calculator

Work out recommended total weight gain through pregnancy, based on your BMI before pregnancy, following the guidelines from the Institute of Medicine (IOM).

Recommended total weight gain
BMI before pregnancy
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How to use the pregnancy weight gain calculator

  1. Enter your weight before pregnancy, in kilograms.
  2. Enter your height, in centimeters.
  3. The calculator works out your pre-pregnancy BMI and shows the recommended total weight gain through pregnancy.

How the recommended weight gain is calculated

The calculator first works out BMI (body mass index) from your weight before pregnancy:

BMI = Weight (kg) ÷ Height (m)²

Your BMI category is then used to find the recommended total weight gain through pregnancy, based on the guidelines from the U.S. Institute of Medicine (IOM):

The idea behind the guidelines is that women with a lower pre-pregnancy BMI have more room for healthy weight gain, while women with a higher pre-pregnancy BMI are recommended a somewhat more limited total weight gain — in both cases to support a healthy pregnancy for both mother and baby.

Important: These are general guidelines, not an individual recommendation. The right amount of weight gain depends on more factors than BMI alone, including whether you're expecting twins, underlying health conditions, and how the pregnancy progresses. Always follow the individual guidance from your midwife or doctor, rather than general tables like this one.
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Frequently asked questions

What happens if I gain more or less than recommended?

Deviating somewhat from the range isn't unusual and doesn't automatically mean something is wrong. Large deviations in either direction should still be discussed with your midwife or doctor, who can assess it in the context of the rest of your prenatal care.

Do these figures also apply to a multiple pregnancy?

No. The IOM has separate, higher recommendations for weight gain in twin and multiple pregnancies. This calculator only shows the recommendations for a single pregnancy. Talk to your midwife or doctor for individual guidance with a multiple pregnancy.

Should I try to lose weight during pregnancy if I have a high BMI?

No, weight loss is not normally recommended during pregnancy, even with a high BMI. The IOM guidelines specify a recommended gain, not a loss, even for the obesity category. Always talk to your midwife or doctor about what's right for your specific situation.

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