Pregnancy Weight Gain Calculator
See the recommended total pregnancy weight gain for your pre-pregnancy BMI, using the Institute of Medicine guidelines for a single baby. Always led by your midwife or doctor.
See the recommended total pregnancy weight gain for your pre-pregnancy BMI, using the Institute of Medicine guidelines for a single baby. Always led by your midwife or doctor.
Recommended total gain
11.5–16 kg (25–35 lb)
Healthy pre-pregnancy weightRanges are the Institute of Medicine guidelines for carrying one baby, based on your weight before pregnancy. Twins and individual medical needs differ, so your midwife or doctor may set a different target for you. This tool is information, not medical advice.
How it works
Enter your pre-pregnancy height and weight to see the recommended total weight gain for a single pregnancy.
The formula and sources
It uses the 2009 Institute of Medicine guidelines, which set total gain by pre-pregnancy BMI: about 12.5 to 18 kg if underweight, 11.5 to 16 kg at a healthy weight, 7 to 11.5 kg if overweight, and 5 to 9 kg with obesity.
Assumptions
- A single baby, not twins.
- Based on your weight before pregnancy.
Limitations
Ranges are for one baby; twins and higher-order pregnancies differ. Healthy gain is individual and is always led by your maternity team.
When to see a doctor
Your midwife or obstetrician guides weight gain in pregnancy. Raise any concerns with them. See our guide to prenatal vitamins for related nutrition.
Primary sources
- Institute of Medicine and National Research Council, Weight Gain During Pregnancy: Reexamining the Guidelines (2009). The guideline this tool implements.
- Current Opinion in Obstetrics and Gynecology, 2009. Sets out the ranges by pre-pregnancy BMI: 28 to 40 lb if underweight (BMI under 18.5), 25 to 35 lb at a healthy weight (18.5 to 24.9), 15 to 25 lb if overweight (25.0 to 29.9), and 11 to 20 lb with obesity (30.0 or above), with second and third trimester rates of about 1.0, 1.0, 0.6 and 0.5 lb a week respectively.
For twins the guidance is provisional: 37 to 54 lb at a healthy pre-pregnancy weight, 31 to 50 lb if overweight and 25 to 42 lb with obesity, with no guideline for underweight women carrying twins. This calculator returns singleton ranges only. Data were also insufficient to set separate ranges for class II and class III obesity, so use the figure your maternity team gives you.
Calculator version 1.0, IOM 2009. Figures and formula last checked 27 July 2026 against the sources above. This tool gives general information and does not replace advice from your own doctor.
Frequently asked questions
How much weight should I gain in pregnancy?
It depends on your pre-pregnancy BMI: roughly 11.5 to 16 kg at a healthy weight, more if you were underweight, and less if you were overweight, for a single baby.
Is the recommended gain different for twins?
Yes. Twin pregnancies have a higher recommended gain, and your maternity team sets the target for you.
What if I gain more or less than the range?
The ranges are guides, not pass or fail. Your midwife or doctor looks at the whole picture, so raise any concerns with them.
When does most pregnancy weight gain happen?
Most gain comes in the second and third trimesters. Early pregnancy usually adds little. See our guide to prenatal vitamins.