Women's Health tool
Pregnancy Weight Gain Calculator
See the recommended pregnancy weight gain in total and by week from your weight before pregnancy, using the Institute of Medicine guidelines. Twins too.
Nothing you enter leaves your device.
Inputs
Results
Enter values to see your results.
Simple steps
How it works
- 01
Choose units and enter your height and your weight before pregnancy.
- 02
Enter your week of pregnancy and whether you expect one baby or twins.
- 03
Select Calculate to see the recommended total and the range for this week.
Good to know
Frequently asked questions
Where do the ranges come from?
From the US Institute of Medicine guidelines (2009), based on your BMI before pregnancy.
How much should I gain in the first trimester?
Usually only 0.5 to 2 kg in total. Most gain happens from the second trimester.
Are there ranges for twins?
Yes, provisional ones for a BMI of 18.5 or more. There is no guidance for twins with a lower BMI.
What if I am outside the range?
Talk to your midwife or doctor. Many things affect weight in pregnancy, and they can advise you.
Should I diet in pregnancy?
Do not start a diet to lose weight during pregnancy without medical advice.
Is anything I enter stored or sent?
No. The calculation runs in your browser. Nothing you type is saved or sent to a server.
How it is calculated
Pre-pregnancy BMI = weight (kg) ÷ height (m)². Total gain (Institute of Medicine, 2009): BMI under 18.5: 12.5–18 kg; 18.5–24.9: 11.5–16 kg; 25–29.9: 7–11.5 kg; 30 or more: 5–9 kg. By week: 0.5–2 kg in the first 13 weeks, then 0.44–0.58, 0.35–0.50, 0.23–0.33 or 0.17–0.27 kg a week. Twins: 17–25, 14–23 or 11–19 kg.
Sources
Last reviewed: October 14, 2026