Pregnancy weight gain calculator
Healthy weight gain in pregnancy for your BMI, week by week.
About this calculator
This pregnancy weight gain calculator shows how much weight is healthy to gain during pregnancy, based on your BMI before you became pregnant.
Enter your height, your weight before pregnancy and how many weeks along you are.
How it works
Uses your BMI before pregnancy to pick the recommended range from the 2009 Institute of Medicine guidelines. Gain is about 0.5 to 2 kg in the first trimester, then a steady weekly amount that depends on your BMI.
Last reviewed:
Worked example
- Units: Feet and pounds
- Height: 5 ft 7 in
- Weight before pregnancy: 137 lb
- Weeks pregnant: 20 weeks
- Expecting: One baby
Recommended total gain: 25 – 35 lb
Common questions
How much weight should I gain during pregnancy?
With a healthy BMI before pregnancy, about 11.5 to 16 kg (25 to 35 lb) for one baby. Less is advised with a higher BMI, and more with a lower one.
Is it normal to lose weight in the first trimester?
Some people lose a little because of morning sickness. Tell your midwife or doctor if you can't keep food down or lose a lot.
What if I'm gaining more than the range?
Small differences are common. Talk to your midwife or doctor, who can look at your diet and activity with you. Don't diet during pregnancy without advice.
Sources and further reading
The story behind it
Where the idea came from: The US Institute of Medicine published its current pregnancy weight gain guidelines in 2009, based on a mother's BMI before pregnancy.
Advice on pregnancy weight has changed a lot over the past century, from strict limits to much looser rules. The 2009 guidelines tied the target to BMI for the first time, using evidence on the health of both mother and baby.
Why you can trust this calculator
- It runs in your browser. Nothing you type into it is sent anywhere.
- The method is explained on this page, so you can check it yourself.
- Free to use, with no sign-up.
- Results are estimates, not medical advice.
- Spotted a mistake? Tell us and we'll look into it.
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