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Pregnancy weight gain calculator
Short answer
The Institute of Medicine's 2009 guidelines base pregnancy weight gain on your BMI before pregnancy. With a normal BMI (18.5–24.9), the recommended total for one baby is 25–35 lb (11.5–16 kg), about 1 lb (0.42 kg) a week in the 2nd and 3rd trimesters. Ranges are higher for underweight and lower for overweight and obesity.
Last reviewed 28 October 20261 published sourcesNot medical advice
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Use your weight before pregnancy, not your weight now. For a single baby; twin ranges are in the table below.
Enter your pre-pregnancy weight and your height.
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| Pre-pregnancy BMI | Total gain | Per week, 2nd–3rd trimester |
|---|---|---|
| Underweight (< 18.5) | 28–40 lb (12.5–18 kg) | 1 lb (1–1.3); 0.51 kg (0.44–0.58) |
| Normal weight (18.5–24.9) | 25–35 lb (11.5–16 kg) | 1 lb (0.8–1); 0.42 kg (0.35–0.5) |
| Overweight (25.0–29.9) | 15–25 lb (7–11.5 kg) | 0.6 lb (0.5–0.7); 0.28 kg (0.23–0.33) |
| Obese (≥ 30.0) | 11–20 lb (5–9 kg) | 0.5 lb (0.4–0.6); 0.22 kg (0.17–0.27) |
| Pre-pregnancy BMI | Total gain |
|---|---|
| Underweight (< 18.5) | Not enough information |
| Normal weight (18.5–24.9) | 37–54 lb (17–25 kg) |
| Overweight (25.0–29.9) | 31–50 lb (14–23 kg) |
| Obese (≥ 30.0) | 25–42 lb (11–19 kg) |
Where the ranges come from
A committee of the Institute of Medicine and National Research Council reexamined the evidence in 2009 and set ranges by pre-pregnancy BMI using the World Health Organization categories: under 18.5, 18.5–24.9, 25.0–29.9 and 30 or more (Institute of Medicine, 2009).
Your midwife, obstetrician or doctor may set a different goal for you. Find your pre-pregnancy BMI with the BMI calculator, and see the folate intake calculator for folate needs in pregnancy.
See what your meals add up to
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Common questions
How much weight should I gain in pregnancy?
Underweight (BMI < 18.5): 28–40 lb (12.5–18 kg); Normal weight (BMI 18.5–24.9): 25–35 lb (11.5–16 kg); Overweight (BMI 25.0–29.9): 15–25 lb (7–11.5 kg); Obese (BMI ≥ 30.0): 11–20 lb (5–9 kg). These are the Institute of Medicine's 2009 ranges for one baby.
How much should I gain in the first trimester?
The weekly rates assume a gain of 1.1–4.4 lb (0.5–2 kg) in the first trimester. Most of the gain comes in the 2nd and 3rd trimesters.
What about twins?
Normal weight: 37–54 lb (17–25 kg); Overweight: 31–50 lb (14–23 kg); Obese: 25–42 lb (11–19 kg). These provisional ranges are for term; there was not enough information to set one for underweight.
Sources
Figures on this page were checked against these publications on 28 October 2026.
- Institute of Medicine and National Research Council. Weight Gain During Pregnancy: Reexamining the Guidelines. Rasmussen KM, Yaktine AL, eds. Washington, DC: The National Academies Press; 2009. nap.nationalacademies.org/read/12584/chapter/2
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