Pregnancy Weight Gain Calculator
Your pregnancy weight gain against the IOM ranges for your BMI, tracked week by week.
Enter your weights, height and week of pregnancy.
Your gain against the recommended range
Week-by-week guide range
| Week | Gain from | Gain to |
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For general information only, not medical advice. Consult a qualified health professional for advice about your situation.
About the Pregnancy Weight Gain Calculator
How much weight is healthy to gain in pregnancy depends on your BMI before pregnancy. The Institute of Medicine (IOM, now the National Academy of Medicine) set the ranges, and the American College of Obstetricians and Gynecologists still bases its advice on them.
Enter your weight before pregnancy, your height, your weight now and how many weeks pregnant you are. The calculator shows your pre-pregnancy BMI group, the recommended total gain, the weekly rate for the second and third trimesters, a guide range for your current week built from those figures — and a chart of your gain against that band, with a week-by-week table you can download. Twin pregnancies use the IOM’s provisional twin ranges.
How to use it
- Choose one baby or twins, and kg · cm or lb · ft/in.
- Enter your weight before pregnancy (or at your first antenatal visit if you do not know it), your height and your weight now.
- Enter how many weeks and days pregnant you are — from the first day of your last period, or as your scan report gives it.
- Read your gain so far and how it compares with the range for this week; the chart and the week-by-week table show the whole pregnancy. Copy or download the result to show your doctor or midwife.
Examples
BMI 22.7 (normal weight) · gained 6 kg · guide range for week 24 is 5.0–7.7 kg — within it · total 11.5–16 kg, 0.35–0.5 kg a week from week 14
Gained 13 lb · guide range for week 24 is 10.8–16.9 lb — within it · total 25–35 lb, 0.8–1 lb a week
IOM provisional total at term: 14–23 kg (31–50 lb)
The IOM 2009 recommendations
By BMI before pregnancy (WHO categories), for a single baby:
- Underweight (below 18.5): total 12.5–18 kg (28–40 lb); 0.44–0.58 kg (1–1.3 lb) a week in the 2nd and 3rd trimesters
- Normal weight (18.5–24.9): 11.5–16 kg (25–35 lb); 0.35–0.50 kg (0.8–1 lb) a week
- Overweight (25.0–29.9): 7–11.5 kg (15–25 lb); 0.23–0.33 kg (0.5–0.7 lb) a week
- Obese (30.0 or more, all classes): 5–9 kg (11–20 lb); 0.17–0.27 kg (0.4–0.6 lb) a week
The IOM’s calculations assume a gain of 0.5–2 kg (1.1–4.4 lb) in the first trimester. Its kilogram and pound figures were rounded separately, so the calculator uses whichever matches the units you choose.
How the weekly band is drawn
The IOM gives a total and a weekly rate, not a value for every week. The shaded guide band therefore uses only the IOM’s own numbers: it rises from zero at week 0 (the first day of the last period) to the assumed first-trimester gain (0.5–2 kg) at the end of week 13, then runs straight to the recommended total at week 40. CDC’s printable weight-gain trackers also end at these totals, though their early weeks are drawn differently. In the first trimester the IOM gives only that 0.5–2 kg total, so the calculator does not treat small differences from the band as a concern there. Treat the band as a guide — what matters most is the overall pattern, which your doctor or midwife will follow.
Twins
The IOM gave provisional twin ranges, the total gain at term (37–42 weeks): normal weight 17–25 kg (37–54 lb), overweight 14–23 kg (31–50 lb) and obese 11–19 kg (25–42 lb). They are the middle half (25th–75th percentile) of the gains of women whose twins were born at 37–42 weeks weighing 2,500 g or more on average. There was not enough information for women who were underweight; CDC’s twin tracker for this group uses 50–62 lb (about 22.7–28.1 kg), based on a study by Luke et al. For triplets or more, CDC advises asking your care provider.
Who the ranges are for
- The IOM wrote them for women in the United States and says they may apply in other developed countries — but they are not intended where women are substantially shorter or thinner than American women, or where good obstetric care is not available.
- The ranges are the same for short women and for all racial and ethnic groups, the IOM found.
- Teenagers use the adult BMI categories.
- ACOG (Committee Opinion 548) asks for BMI to be worked out at the first prenatal visit, for appropriate gain, diet and exercise to be discussed, and for individual care when an overweight or obese woman gains less than recommended but her baby is growing well.
Sources
- Institute of Medicine and National Research Council. Weight Gain During Pregnancy: Reexamining the Guidelines, Summary and Table S-1; and the report brief
- ACOG. Weight Gain During Pregnancy, Committee Opinion 548
- CDC. Weight Gain During Pregnancy and its printable weight-gain trackers
Limitations
- A guide for healthy pregnancies, not medical advice: your doctor or midwife may set a different target for you.
- The band between the IOM’s published totals and rates is an approximation, not a published week-by-week standard.
- Twin targets are totals for the whole pregnancy, so the calculator can only compare your gain with them from 37 weeks.
- Weights of 30–250 kg before pregnancy (30–300 kg now), heights of 120–220 cm and weeks 0–42 are accepted.
Privacy
Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.
Frequently asked questions
How much weight should I gain during pregnancy?
It depends on your BMI before pregnancy: 12.5–18 kg if you were underweight, 11.5–16 kg at a normal weight, 7–11.5 kg if overweight and 5–9 kg if obese (IOM 2009, one baby). Twins need more: 17–25 kg from a normal weight.
How much should I gain each week?
Little in the first trimester — the IOM assumes 0.5–2 kg in total. From the second trimester, about 0.35–0.50 kg a week at a normal BMI, 0.44–0.58 kg if you were underweight, 0.23–0.33 kg if overweight and 0.17–0.27 kg if obese.
I am gaining faster than the range. Should I diet?
Talk to your doctor or midwife first. CDC’s weight-gain trackers suggest small changes to diet and physical activity to get back on track, and say you should not try to lose weight during pregnancy.
Are there different BMI cut-offs for Indian or Asian women?
The IOM uses the WHO BMI categories for everyone and found no reason to change the ranges for racial or ethnic groups. It does say its ranges are not meant for places where women are substantially shorter or thinner than American women, so follow the advice of your own doctor or midwife.
What weight do I use if I do not know my weight before pregnancy?
Use the weight recorded at your first antenatal visit, ideally in the first trimester. If that was later, the result will understate how much you have gained.