Pregnancy Weight Gain Calculator
See the healthy weight gain range for your BMI and how many weeks pregnant you are.
Pregnancy weight gain calculator
Healthy weight gain ranges from the US Institute of Medicine (2009), based on your weight before pregnancy.
Quick answer
Healthy pregnancy weight gain depends on pre-pregnancy BMI: 12.5–18 kg if underweight, 11.5–16 kg at a healthy weight, 7–11.5 kg if overweight and 5–9 kg if obese (Institute of Medicine, 2009). Most of the gain comes after the first trimester.
How the range is calculated
Your pre-pregnancy BMI (weight ÷ height²) sets your total recommended gain. In the first trimester a gain of about 0.5–2 kg is expected; after week 13 the calculator adds the recommended weekly rate for your BMI group to show a healthy range for your current week.
These are the US Institute of Medicine (now National Academy of Medicine) 2009 guidelines, used widely around the world. Indian guidance often uses lower BMI cut-offs for South Asian women, so your doctor may set a slightly different target.
Recommended weight gain (IOM 2009)
Total gain and weekly rate in the second and third trimesters.
| Pre-pregnancy BMI | Total gain (single baby) | Twins | Per week after 13 weeks |
|---|---|---|---|
| Under 18.5 | 12.5–18 kg | Ask your doctor | 0.44–0.58 kg |
| 18.5–24.9 | 11.5–16 kg | 17–25 kg | 0.35–0.5 kg |
| 25–29.9 | 7–11.5 kg | 14–23 kg | 0.23–0.33 kg |
| 30 or more | 5–9 kg | 11–19 kg | 0.17–0.27 kg |
Frequently asked questions
How much weight should I gain in the first trimester?
Usually only 0.5–2 kg. Some people lose a little because of nausea, which is common.
Is it safe to lose weight during pregnancy?
Don't diet to lose weight in pregnancy unless your doctor advises it. Focus on nutritious food and regular activity.
Where does pregnancy weight go?
Into the baby, placenta, amniotic fluid, extra blood and fluid, breast tissue, a larger womb and some fat stores for breastfeeding.
Why might my doctor give a different target?
Doctors consider your health, your baby's growth and, in India, often use Asian BMI cut-offs.
Talk to your doctor if you
- Gain or lose weight suddenly, especially with swelling of the face or hands
- Can't keep food or fluids down
- Are worried about eating, or have a history of an eating disorder
In an emergency call 112 (India) or 911 (US). This tool gives general information, not medical advice.
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