Pregnancy Weight Gain Calculator
See how much weight the Institute of Medicine recommends gaining in pregnancy for your pre-pregnancy BMI — for one baby or twins — and check how you are tracking week by week.
Check your pregnancy weight gain
Recommended weight gain
| BMI before pregnancy | One baby — total | Per week, 2nd & 3rd trimester | Twins — total |
|---|---|---|---|
| Underweight (under 18.5) | 12.5–18 kg | 0.44–0.58 kg | No guideline |
| Healthy (18.5–24.9) | 11.5–16 kg | 0.35–0.50 kg | 17–25 kg |
| Overweight (25.0–29.9) | 7–11.5 kg | 0.23–0.33 kg | 14–23 kg |
| Obese (30 and over) | 5–9 kg | 0.17–0.27 kg | 11–19 kg |
How it is calculated
weight before pregnancy (kg) ÷ height (m)²
suggested gain rises evenly to 0.5–2 kg by the end of week 13
then rises evenly to the total range at week 40
The by-week range is an even-pace guide built from the published totals, so it always ends exactly on the recommended total. Real weight gain is rarely perfectly even.
The twin ranges are provisional; there is not enough evidence for a twin range for women who were underweight. This calculator is not suitable for triplets or more.
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For general information only — not medical advice, diagnosis or treatment. These calculators use population formulas that cannot account for every individual, and are meant for adults unless stated. Always speak to a qualified doctor about your health, and never delay seeking care because of a result here.