See the recommended weight gain in pregnancy for your pre-pregnancy BMI.
Calculated privately in your browser.
How much weight should you gain during pregnancy?
Recommended total gain depends on pre-pregnancy BMI (single baby): underweight 12.5–18 kg, normal 11.5–16 kg, overweight 7–11.5 kg, obese 5–9 kg. For example, a normal BMI of 22 suggests about 11.5–16 kg (25–35 lb). Most gain happens in the second and third trimesters; carrying twins differs.
Understanding your result
Most gain happens in the second and third trimesters. Guidelines are for a single baby; carrying twins is different.
Formula and method
Recommended total gain by BMI: underweight 12.5–18 kg, normal 11.5–16 kg, overweight 7–11.5 kg, obese 5–9 kg (single baby).
Assumptions and limitations
These ranges are general Institute of Medicine guidelines for a single baby, not medical advice, and every pregnancy is different. They do not apply to twins and cannot reflect your health, history or how your pregnancy is progressing. Use them as a reference point and follow the guidance of your midwife or doctor.
Worked example
At a pre-pregnancy BMI of 22 (normal), the recommended total gain is about 11.5–16 kg (25–35 lb).
How to use this tool
- Enter your pre-pregnancy weight and height.
- Optionally add your current week.
- Press Calculate.
About the Pregnancy Weight Gain Calculator
The Pregnancy Weight Gain Calculator shows the recommended total weight gain for your pre-pregnancy BMI, using Institute of Medicine guidelines, plus a target for your current week.
Who should use this tool
Expectant parents who want to see the recommended total pregnancy weight gain for their pre-pregnancy BMI, along with a target for their current week. Based on Institute of Medicine guidelines for a single baby, it offers a general reference to discuss with a midwife or doctor.
Benefits
- Shows recommended total gain for your pre-pregnancy BMI
- Based on established Institute of Medicine guidelines
- Gives a target for your current pregnancy week
- Fast enough to rerun as many times as you like
Practical use cases
- Checking the recommended range for your BMI category
- Seeing a rough target for your current week
- Preparing questions for a midwife appointment
- Understanding how gain is spread across trimesters
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Frequently asked questions
Are these guidelines for twins?
No — they’re for a single baby. Recommended gain for twins is higher; ask your provider for personalised guidance.
Why is recommended weight gain based on pre-pregnancy BMI?
The Institute of Medicine guidelines set different ranges depending on whether your pre-pregnancy weight was in the underweight, normal, overweight or obese category. Starting point affects how much additional gain is generally recommended. The tool uses your pre-pregnancy BMI to show the range that applies, as a reference to discuss with your care provider.
When does most pregnancy weight gain happen?
As the tool notes, most gain typically occurs in the second and third trimesters rather than early on. This is why the week-by-week target rises over time. Individual patterns vary, and your midwife or doctor can advise on what is appropriate for your particular pregnancy.