Pregnancy Weight Gain Calculator
Healthy pregnancy weight gain by BMI and week (IOM 2009)
| BMI before pregnancy | One baby | Per week (from week 14) | Twins |
|---|---|---|---|
| Underweight (below 18.5) | 12.5–18 kg | 0.44–0.58 kg | Not enough data |
| Normal weight (18.5–24.9) (you) | 11.5–16 kg | 0.35–0.5 kg | 17–25 kg |
| Overweight (25–29.9) | 7–11.5 kg | 0.23–0.33 kg | 14–23 kg |
| Obese (30 and above) | 5–9 kg | 0.17–0.27 kg | 11–19 kg |
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For general information only, not medical advice. Talk to a doctor or a qualified professional about your health. Terms of use
How to Use
- Enter your Height and your Weight before pregnancy. The tool works out your pre-pregnancy BMI from these.
- Enter the Week of pregnancy from your scan or doctor's card (completed weeks) and your Weight now.
- Choose One baby or Twins.
- You'll see how much you've gained, the recommended total for your BMI and the usual range for your current week.
- The chart shows the recommended range week by week with your own point on it. Download the PDF to show your doctor at the next check-up.
How much weight to gain in pregnancy
Gaining the right amount of weight in pregnancy supports your baby's growth and lowers the risk of problems for both of you. Too little gain is linked with low birth weight and preterm birth, which are still common in India. Too much is linked with gestational diabetes, high blood pressure, a big baby, caesarean delivery and weight that stays on after birth. This pregnancy weight gain calculator uses the Institute of Medicine (IOM) 2009 guidelines, the most widely used reference, to show the recommended range for you and where you are today.
Step 1: your BMI before pregnancy
A woman who weighed 55 kg before pregnancy and is 158 cm tall has a BMI of 55 ÷ (1.58 × 1.58) = 22.0, which is in the normal range.
Step 2: the IOM ranges
| BMI before pregnancy | Total gain, one baby | Per week from week 14 | Total gain, twins |
|---|---|---|---|
| Underweight (below 18.5) | 12.5–18 kg | 0.44–0.58 kg | Not enough data |
| Normal (18.5–24.9) | 11.5–16 kg | 0.35–0.50 kg | 17–25 kg |
| Overweight (25–29.9) | 7–11.5 kg | 0.23–0.33 kg | 14–23 kg |
| Obese (30 and above) | 5–9 kg | 0.17–0.27 kg | 11–19 kg |
The weekly rates assume a gain of 0.5 to 2 kg in the first trimester (weeks 1 to 13). The twin figures are provisional, and the IOM did not give weekly rates for twins.
Step 3: the range for your week
After week 13: (0.5 + extra weeks × low rate) to (2 + extra weeks × high rate)
For our example at 20 weeks, that's 7 weeks after the first trimester: 0.5 + 7 × 0.35 = 2.95 kg at the low end and 2 + 7 × 0.5 = 5.5 kg at the high end. If she weighs 60 kg now, she has gained 5 kg, inside the range. By 40 weeks her total should land somewhere around 11.5 to 16 kg.
A note for Indian women
The IOM uses the WHO BMI classes. Indian guidelines for adults count a BMI of 23 to 24.9 as overweight and 25 or more as obese, because Indians tend to develop diabetes and heart disease at lower weights. If your BMI is between 23 and 25, ask your doctor whether to aim for the normal or the overweight range. Gestational diabetes is common in India, and many hospitals test every pregnant woman for it.
Practical tips
- Weigh yourself once a week, at the same time of day, on the same scale.
- "Eating for two" isn't needed. ICMR-NIN (2020) puts the extra energy need in pregnancy at about 350 kcal a day, roughly one extra small meal.
- Take the iron, folic acid and calcium tablets your doctor or ANM gives you.
- Keep moving. Walking is safe for most women; ask your doctor before starting anything new.
This is a guide based on population averages. Your doctor, who knows your history and scans, will set the target that's right for you.