Pregnancy Weight Gain Calculator

Enter your height, pre-pregnancy weight, and current week to find your recommended weight gain range according to IOM 2009 guidelines.

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Recommended Weight Gain by BMI Category

BMI Category VKİ Singleton Twins
Underweight< 18.512.5 – 18 kg—
Normal weight18.5 – 24.911.5 – 16 kg17 – 25 kg
Overweight25.0 – 29.97 – 11.5 kg14 – 23 kg
Obese≥ 305 – 9 kg11 – 19 kg

Formula

VKİ = kg ÷ m²
Weight (kg) divided by height squared (m²)

This calculator uses the IOM (Institute of Medicine) 2009 guidelines. Results are for general information only and do not replace medical advice.

How to use?

  1. 1
    Enter your details Enter your height (cm), pre-pregnancy weight (kg), and current pregnancy week.
  2. 2
    Select pregnancy type Choose singleton or twin pregnancy. Recommended ranges differ for twin pregnancies.
  3. 3
    Review your results Check your total and weekly recommended ranges and the week-by-week table based on your BMI.

FAQ

How much weight should I gain during pregnancy?
According to IOM 2009, normal-weight women (BMI 18.5–24.9) should gain 11.5–16 kg. Underweight women: 12.5–18 kg; overweight: 7–11.5 kg; obese: 5–9 kg.
How much weight gain per week during pregnancy?
For normal-weight women, about 0.36–0.45 kg per week in the 2nd and 3rd trimesters. The first trimester total is usually only 0.5–2 kg.
How does BMI affect pregnancy weight gain?
A lower pre-pregnancy BMI means more total weight gain is recommended; a higher BMI means less. This balances maternal energy reserves with fetal needs.
What is the recommended weight gain for twin pregnancy?
For normal-weight women carrying twins: 17–25 kg. Overweight: 14–23 kg. Obese: 11–19 kg.
Is gaining too much weight during pregnancy harmful?
Yes. Excessive weight gain increases the risk of gestational diabetes, preeclampsia, C-section, and macrosomia. Staying within guidelines benefits both mother and baby.
Are results stored?
No. All calculations run in your browser. No data is sent to any server.

How Is Pregnancy Weight Gain Calculated?

Pregnancy weight gain is calculated using your pre-pregnancy Body Mass Index (BMI). BMI = Weight (kg) ÷ Height² (m²). Based on your BMI category, the IOM (Institute of Medicine) 2009 guidelines provide a total and weekly recommended weight gain range.

Recommended Weight Gain by BMI Category

Underweight women (BMI < 18.5): 12.5–18 kg; Normal weight (BMI 18.5–24.9): 11.5–16 kg; Overweight (BMI 25–29.9): 7–11.5 kg; Obese (BMI ≥ 30): 5–9 kg. For twin pregnancies, ranges are higher.

Trimester-by-Trimester Breakdown

During the first trimester (weeks 1–13), total gain is usually 0.5–2 kg. In the second and third trimesters (weeks 14–40), normal-weight women should gain approximately 0.36–0.45 kg per week.

Important Disclaimer

This tool is for general informational purposes only. Always consult your OB-GYN or registered dietitian for personalised advice.

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