Pregnancy Weight Gain Calculator

Q: Why does recommended gain vary by BMI?

Women with higher pre-pregnancy BMI already have greater energy reserves. Gaining less weight reduces risks such as gestational diabetes, large-for-gestational-age babies, and caesarean delivery. Underweight women need more gain to ensure the baby has sufficient nutrients.

Q: When should most weight be gained?

Typically only 0.5–2 kg is gained in the first trimester. Most weight gain happens in the second and third trimesters roughly 0.4–0.5 kg per week for normal-weight women carrying a single baby.

Q: Does this apply to twin pregnancies?

Yes! Our calculator adjusts automatically for twins and triplets. For twins, normal-weight women should aim for 16.8–24.5 kg total, which is significantly higher than a singleton pregnancy.

🤰 Pregnancy

Find recommended weight gain based on your pre-pregnancy BMI per IOM guidelines.

Pre-Pregnancy Weight

Height

Pregnancy Type

Current Week

wks

Weight Gain Results

Pre-Pregnancy BMI

—

— Category

⚖️ Recommended Gain

📊 IOM Guidelines (Single)

Underweight <18.5

12.5–18 kg

Normal 18.5–24.9

11.5–16 kg

Overweight 25–29.9

7–11.5 kg

Obese ≥30

5–9 kg

Saving…

Gaining the right amount of weight during pregnancy supports your baby’s healthy development and reduces risks for both mother and child. Our Pregnancy Weight Gain Calculator gives you a personalised recommended weight gain range based on your pre-pregnancy BMI, using the latest Institute of Medicine (IOM) guidelines.

Whether you are carrying a single baby, twins, or triplets, this tool adjusts the recommendation accordingly giving you clear, evidence-based targets to discuss with your doctor or midwife.

How to Use This Calculator

Enter your pre-pregnancy weight in kilograms (your weight before you became pregnant).
Enter your height in centimetres so we can calculate your pre-pregnancy BMI.
Select your pregnancy type single baby, twins, or triplets.
Enter your current week of pregnancy (optional, for context).
Click “Calculate Weight Range” to see your personalised recommended weight gain.

IOM Recommended Weight Gain (Single Baby)

Underweight (BMI < 18.5): Gain 12.5 – 18 kg during pregnancy
Normal Weight (BMI 18.5–24.9): Gain 11.5 – 16 kg during pregnancy
Overweight (BMI 25–29.9): Gain 7 – 11.5 kg during pregnancy
Obese (BMI ≥ 30): Gain 5 – 9 kg during pregnancy

Frequently Asked Questions

Why does recommended gain vary by BMI?

Women with higher pre-pregnancy BMI already have greater energy reserves. Gaining less weight reduces risks such as gestational diabetes, large-for-gestational-age babies, and caesarean delivery. Underweight women need more gain to ensure the baby has sufficient nutrients.

When should most weight be gained?

Typically only 0.5–2 kg is gained in the first trimester. Most weight gain happens in the second and third trimesters roughly 0.4–0.5 kg per week for normal-weight women carrying a single baby.

Does this apply to twin pregnancies?

Yes! Our calculator adjusts automatically for twins and triplets. For twins, normal-weight women should aim for 16.8–24.5 kg total, which is significantly higher than a singleton pregnancy.

⚠️ Disclaimer: Weight gain recommendations during pregnancy should always be discussed with your OB-GYN or midwife. This tool provides general IOM guidelines and does not replace personalised medical advice.