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How much weight should you gain?
There's no single right number — healthy pregnancy weight gain depends on your weight before pregnancy. Someone who started underweight should gain more than someone who started with obesity, because the goal is a healthy baby without unnecessary risk to either of you.
The widely used guidelines come from the U.S. Institute of Medicine (IOM), which set recommended ranges based on pre-pregnancy BMI.
How this calculator works
Enter your height and your pre-pregnancy weight, and we calculate your starting BMI, then show the IOM recommended total gain for a single baby:
| Pre-pregnancy BMI | Recommended gain |
|---|---|
| Underweight (<18.5) | 12.5–18 kg (28–40 lb) |
| Healthy (18.5–24.9) | 11.5–16 kg (25–35 lb) |
| Overweight (25–29.9) | 7–11.5 kg (15–25 lb) |
| Obesity (≥30) | 5–9 kg (11–20 lb) |
Add your current week and the calculator also estimates how much you'd typically have gained by that point.
Where the weight goes
Very little of pregnancy weight is fat. A typical gain is spread across the baby (about 3–3.5 kg), the placenta, amniotic fluid, extra blood and fluid, a larger uterus and breasts, and some maternal energy stores for breastfeeding. That's why steady, moderate gain — not dieting — is the goal.
Gaining at a healthy rate
Most weight is gained in the second and third trimesters — often only about 0.5–2 kg in the first trimester, then a steady weekly rise. Focus on nutrient-dense food rather than "eating for two": the extra energy needed is smaller than many expect, especially early on.
Helpful tools
Eat well for you and your baby through every trimester.
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Frequently asked questions
How much weight should I gain in the first trimester?
Usually only about 0.5–2 kg (1–4.5 lb). Most pregnancy weight is gained steadily through the second and third trimesters.
What if I was overweight before pregnancy?
The IOM recommends a smaller gain of about 7–11.5 kg (15–25 lb) for overweight and 5–9 kg (11–20 lb) for obesity. Your provider can give tailored advice.
Is the recommendation different for twins?
Yes — carrying twins requires more weight gain. These figures are for a single baby, so follow your provider's specific guidance for a multiple pregnancy.
Is it safe to gain very little weight?
Gaining too little can raise the risk of a low-birth-weight baby. Even if you started with a higher BMI, some gain is expected — discuss your plan with your provider.