Pregnancy Weight Gain Calculator

How much weight should I gain during pregnancy?

Recommended pregnancy weight gain depends on your pre-pregnancy BMI. For a singleton pregnancy: underweight women (BMI < 18.5) should gain 12.5–18 kg (28–40 lbs), normal weight (BMI 18.5–24.9) should gain 11.5–16 kg (25–35 lbs), overweight (BMI 25–29.9) should gain 7–11.5 kg (15–25 lbs), and obese women (BMI ≥ 30) should gain 5–9 kg (11–20 lbs). These guidelines come from ACOG and the Institute of Medicine.

How much weight should I gain per week during pregnancy?

In the first trimester (weeks 1–13), weight gain is typically 0.5–2 kg total. In the second and third trimesters, normal-weight women should gain about 0.35–0.50 kg per week, underweight women 0.44–0.58 kg per week, overweight women 0.23–0.33 kg per week, and obese women 0.17–0.27 kg per week. These are averages — some weekly variation is normal.

Is pregnancy weight gain different for twins?

Yes. Weight gain recommendations are higher for twin pregnancies: normal-weight women should gain 17–25 kg (37–55 lbs), overweight women 14–23 kg (31–51 lbs), and obese women 11–19 kg (24–42 lbs). Underweight women with twins should gain 23–28 kg. Twin pregnancy guidelines are considered provisional by the IOM due to limited data.

What happens if I gain too much or too little weight during pregnancy?

Gaining too little weight increases the risk of preterm birth and low birth weight. Gaining too much increases the risk of gestational diabetes, high blood pressure, cesarean delivery, and difficulty losing weight after pregnancy. Both the mother and baby benefit when weight gain is within the recommended range. Talk to your healthcare provider if you are concerned about your weight gain.

How is BMI calculated for pregnancy weight gain?

BMI used for pregnancy weight gain guidelines is calculated from your PRE-PREGNANCY weight — not your current weight. The formula is: BMI = weight (kg) ÷ height (m)². For example, 65 kg and 165 cm gives a BMI of 65 ÷ (1.65)² = 23.9, which falls in the normal-weight category (18.5–24.9).

When should I talk to my doctor about pregnancy weight gain?

Consult your healthcare provider if you gain more than 1.5 kg in a single week (may indicate fluid retention or preeclampsia), if you are not gaining any weight by the second trimester, if your total gain is significantly above or below guidelines, or if you have a BMI over 35. This calculator provides general guidance based on ACOG standards — it is not medical advice.