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Browse all calculatorsEnter height, weight before pregnancy and weeks pregnant to see the Institute of Medicine (2009) total and the range for your week. Published ranges, not advice: only a midwife or doctor advises on weight gain in pregnancy.
Only a midwife or doctor can advise on weight gain in pregnancy. These are published ranges for groups of women, not targets for you. Advice differs with health conditions, age and weight history. This page gives no diet or weight-loss advice.
The ranges are for adult women in the BMI groups the IOM uses. The IOM report discusses adolescents under 20 separately, so if you are under 20 a midwife or doctor can say which range applies.
This is a general estimate for educational use. It is not medical advice, a diagnosis or a treatment plan. Talk to a doctor, midwife or other qualified professional before you change your diet, exercise or health care.
Straight line from the published first-trimester figure (at 14 weeks 0 days) to the published total (at 40 weeks). A row for 20 weeks means 20 weeks 0 days.
| Week | Gain so far (kg) | Weight (kg) |
|---|
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The Institute of Medicine (IOM) 2009 total gain for one baby depends on BMI before pregnancy: 28 to 40 lb below 18.5, 25 to 35 lb for 18.5 to 24.9, 15 to 25 lb for 25.0 to 29.9, and 11 to 20 lb from 30.0. This calculator finds the group and the range for your week.
The result updates as you type, in metric or US units. It works out your BMI before pregnancy, picks the matching IOM group, shows the total for the whole pregnancy and a range for your week, and, if you add the weight you have now, says whether the gain so far is within, below or above that range. Only a midwife or doctor can advise on weight gain in pregnancy. To count weeks and days first, use the pregnancy calculator or the due date calculator. For other everyday sums see the free online calculators.
| Height and weight | IOM group (BMI) | Total gain | At 28 weeks |
|---|---|---|---|
| 165 cm, 65 kg BMI 23.9 |
18.5 to 24.9 | 11.5 to 16 kg 25 to 35 lb |
6.4 to 9.5 kg 14.0 to 20.9 lb |
| 160 cm, 45 kg BMI 17.6 |
below 18.5 | 12.5 to 18 kg 28 to 40 lb |
7.0 to 10.6 kg 15.6 to 23.6 lb |
| 170 cm, 80 kg BMI 27.7 |
25.0 to 29.9 | 7 to 11.5 kg 15 to 25 lb |
4.0 to 7.1 kg 8.6 to 15.5 lb |
| 5 ft 4 in, 190 lb BMI 32.6 |
30.0 and above | 5 to 9 kg 11 to 20 lb |
2.9 to 5.8 kg 6.4 to 12.8 lb |
| 170 cm, 95 kg BMI 32.9 |
30.0 and above | 5 to 9 kg 11 to 20 lb |
2.9 to 5.8 kg 6.4 to 12.8 lb |
The first answer is already on screen. Change any number and the ranges update at once, with no Calculate button.
Metric uses centimetres and kilograms. US uses feet, inches and pounds. Pick one baby or twins. Switching units converts your numbers, so the same person stays on screen.
The weight before pregnancy sets the BMI group. Weeks pregnant, and optional days, set the week. Heights from 100 to 230 cm and weights from 30 to 300 kg are accepted.
The big number is the published total for the whole pregnancy. Below it are the range for your week, the first-trimester figure and the weekly rate.
The gain so far is set against the range in neutral words: within, below or above. Nothing is saved, and a midwife or doctor decides what it means.
Figures as printed by the Institute of Medicine (2009) and the CDC. The second column holds the labels those sources use for the BMI groups. They name groups on a chart and say nothing about health.
| BMI before pregnancy | Label in the sources | Total gain (lb) | Total gain (kg) | lb a week: mean (range) | kg a week: mean (range) |
|---|---|---|---|---|---|
| below 18.5 | Underweight | 28 to 40 | 12.5 to 18 | 1 (1 to 1.3) | 0.51 (0.44 to 0.58) |
| 18.5 to 24.9 | Normal weight | 25 to 35 | 11.5 to 16 | 1 (0.8 to 1) | 0.42 (0.35 to 0.50) |
| 25.0 to 29.9 | Overweight | 15 to 25 | 7 to 11.5 | 0.6 (0.5 to 0.7) | 0.28 (0.23 to 0.33) |
| 30.0 and above | Obese | 11 to 20 | 5 to 9 | 0.5 (0.4 to 0.6) | 0.22 (0.17 to 0.27) |
In every group the IOM table assumes a gain of 0.5 to 2 kg (1.1 to 4.4 lb) in the first trimester. The CDC page prints the top group as 30.0 to 39.9; the IOM table prints it as 30.0 and above, and this calculator uses 30.0 and above.
| BMI before pregnancy | Label in the sources | Total gain (lb) | Total gain (kg) | Source |
|---|---|---|---|---|
| below 18.5 | Underweight | No IOM range | No IOM range | IOM: too little information. CDC lists 50 to 62 lb and marks it as not from the IOM. |
| 18.5 to 24.9 | Normal weight | 37 to 54 | 17 to 25 | IOM, provisional |
| 25.0 to 29.9 | Overweight | 31 to 50 | 14 to 23 | IOM, provisional |
| 30.0 and above | Obese | 25 to 42 | 11 to 19 | IOM, provisional |
The IOM gives no first-trimester figure, weekly rate or range for a single week for twins, so this calculator shows the total only and does not compare a weight for twins. Where the sources give no range, the table says so.
The IOM does not publish a range for every week. From 14 weeks 0 days this page draws a straight line between two published figures: the first-trimester gain and the total at 40 weeks. Each cell shows the pound range with the kilogram range beneath, each worked from its own published column.
| Week | Below 18.5 | 18.5 to 24.9 | 25.0 to 29.9 | 30.0 and above |
|---|---|---|---|---|
| 14 weeks | 1.1 to 4.4 lb 0.5 to 2.0 kg |
1.1 to 4.4 lb 0.5 to 2.0 kg |
1.1 to 4.4 lb 0.5 to 2.0 kg |
1.1 to 4.4 lb 0.5 to 2.0 kg |
| 16 weeks | 3.2 to 7.1 lb 1.4 to 3.2 kg |
2.9 to 6.8 lb 1.3 to 3.1 kg |
2.2 to 6.0 lb 1.0 to 2.7 kg |
1.9 to 5.6 lb 0.8 to 2.5 kg |
| 20 weeks | 7.3 to 12.6 lb 3.3 to 5.7 kg |
6.6 to 11.5 lb 3.0 to 5.2 kg |
4.3 to 9.2 lb 2.0 to 4.2 kg |
3.4 to 8.0 lb 1.5 to 3.6 kg |
| 24 weeks | 11.4 to 18.1 lb 5.1 to 8.2 kg |
10.3 to 16.2 lb 4.7 to 7.4 kg |
6.4 to 12.3 lb 3.0 to 5.7 kg |
4.9 to 10.4 lb 2.2 to 4.7 kg |
| 28 weeks | 15.6 to 23.6 lb 7.0 to 10.6 kg |
14.0 to 20.9 lb 6.4 to 9.5 kg |
8.6 to 15.5 lb 4.0 to 7.1 kg |
6.4 to 12.8 lb 2.9 to 5.8 kg |
| 32 weeks | 19.7 to 29.0 lb 8.8 to 13.1 kg |
17.6 to 25.6 lb 8.1 to 11.7 kg |
10.7 to 18.7 lb 5.0 to 8.6 kg |
8.0 to 15.2 lb 3.6 to 6.8 kg |
| 36 weeks | 23.9 to 34.5 lb 10.7 to 15.5 kg |
21.3 to 30.3 lb 9.8 to 13.8 kg |
12.9 to 21.8 lb 6.0 to 10.0 kg |
9.5 to 17.6 lb 4.3 to 7.9 kg |
| 40 weeks | 28.0 to 40.0 lb 12.5 to 18.0 kg |
25.0 to 35.0 lb 11.5 to 16.0 kg |
15.0 to 25.0 lb 7.0 to 11.5 kg |
11.0 to 20.0 lb 5.0 to 9.0 kg |
Check against the weekly rate: for BMI 18.5 to 24.9, the first-trimester figure plus the published weekly rate over 26 weeks (14 to 40) gives 21.9 to 30.4 lb at 40 weeks, while the published total is 25 to 35 lb. The weekly rates and the totals are published separately and do not add up exactly, so the line is drawn to the totals. The kilogram figures show the same gap (9.6 to 15.0 kg against 11.5 to 16 kg). The sources give no figures after 40 weeks.
Many pages ask for height, weight and week, then show a single range with no explanation. These are the differences that matter when you want to understand the number.
| Feature | Basic calculator | This calculator |
|---|---|---|
| Method | Some show a range for your week with no stated curve | The straight line is written out step by step, with the published figures it starts from |
| Wording | Often attaches a verdict word to the weight | Only within, below or above the published range, and a midwife or doctor decides |
| Twins | Some show a full week-by-week curve with no stated source | Total only where the IOM gives one, and a plain statement where it gives none |
| Units | Often one system | Metric or US, each range worked from its own published column |
| Sources | Rarely named | CDC and IOM pages named, with the BMI cut-offs as printed |
| Speed | Often needs a Calculate button | Updates as you type, with an answer on first load |
| Sharing | Rare | Copy the result, or share a link that opens with the same inputs |
A leaflet may quote an IOM or CDC range. Type your numbers to see which BMI group it refers to and what the range is for each week.
Copy the result, or share a link, so the numbers are in front of you when you talk with your midwife or doctor.
The source gives one figure for the whole trimester. The calculator shows that figure and explains why it does not give a weekly range yet.
Switch between the two to see the published totals side by side, and which groups have no IOM range for twins.
Use either system. Each range comes from its own published column, so the figures match the source.
Not sure of the week? Work it out from a last period or due date with the pregnancy calculator, then come back with the number of weeks.
The ranges describe groups of women. They are published guidance, not a rule for any one person.
Only a midwife or doctor can advise on weight gain in pregnancy. This calculator gives no diet or weight-loss advice. Advice differs with health conditions, age and weight history, so use the numbers as a starting point for that conversation.
The ranges are for adult women. The IOM report discusses adolescents under 20 on their own: it found too little evidence to change its guidelines for them and noted that younger adolescents often need to gain more. The age calculator works out an age from a birth date.
The IOM based its BMI groups on the World Health Organization cut-offs. The calculator uses the weight you enter as the weight before pregnancy, not the weight now.
Health conditions, age and previous weight can all change the advice a midwife or doctor gives. The published ranges describe groups and are not targets.
The IOM says its guidelines are intended for women in the United States and may apply in other developed countries. It does not intend them for places where women are substantially shorter or thinner, or where adequate obstetric services are unavailable.
The 1990 IOM report had recommended the lower end of the range for women under 157 cm. The 2009 committee found too little evidence to keep that change, so this calculator makes none.
Weeks are completed weeks from the first day of the last period. The CDC trimester definitions used here put the first trimester up to 13 weeks 6 days and the second from 14 weeks 0 days. The due date calculator shows the estimated due date.
The ranges are the ones the IOM and CDC publish for groups. They are not a goal, a limit or a measure of how a pregnancy is going. The CDC page asks readers to work with a health care provider on weight gain goals.
The IOM gives a first-trimester figure, a total and a weekly rate, not a range for each week. The weekly line is this page construction from those figures, and the sources give nothing after 40 weeks.
No range is shown for a single week of a twin pregnancy, for underweight twins from the IOM, or for adolescents under 20. The IOM report summary explains each limit in its own words.
Every range, cut-off and rate on this page is as printed in the first two sources below. The CDC page is dated 15 May 2024 and lists the same one-baby ranges as the IOM table; its underweight twin figure of 50 to 62 lb carries a note that it is not from the IOM. The trimester boundaries come from the third source. The week-by-week line is this page construction and is not published by any of them.
Short answers about the IOM ranges, the BMI groups and the limits of this calculator.
The Institute of Medicine (IOM) ranges for one baby, repeated by the CDC, depend on BMI before pregnancy: 28 to 40 lb below 18.5, 25 to 35 lb from 18.5 to 24.9, 15 to 25 lb from 25.0 to 29.9, and 11 to 20 lb at 30.0 and above. These are published ranges for groups of women, so a midwife or doctor decides what applies to any one person.
BMI is the weight before pregnancy in kilograms divided by the height in metres squared. The result is rounded to one decimal and compared with the cut-offs the IOM and CDC print: below 18.5, 18.5 to 24.9, 25.0 to 29.9, and 30.0 and above.
The IOM table assumes a gain of 0.5 to 2 kg (1.1 to 4.4 lb) over the whole first trimester, the same for every group. The source gives one figure for the trimester, not a range for each week, so before 14 weeks 0 days this page checks only the top of it.
The IOM table gives a mean and a range for each group, in pounds a week: 1 (1 to 1.3) below BMI 18.5, 1 (0.8 to 1) from 18.5 to 24.9, 0.6 (0.5 to 0.7) from 25.0 to 29.9, and 0.5 (0.4 to 0.6) at 30.0 and above. The kilogram rates are printed as a separate column.
From 14 weeks 0 days the page draws a straight line between the published first-trimester figure and the published total at 40 weeks. For BMI 18.5 to 24.9 in kilograms that is 0.5 to 2 at 14 weeks and 11.5 to 16 at 40 weeks, so at 28 weeks it is 6.4 to 9.5 kg. The IOM does not publish a range for each week, so the line is built from its figures.
They compare the gain so far with the range for that week and say nothing more. A gain outside the range is not a diagnosis and a gain inside it is not a guarantee. A midwife or doctor decides what a number means for the person.
For twins the IOM gives provisional totals only: 37 to 54 lb for BMI 18.5 to 24.9, 31 to 50 lb for 25.0 to 29.9, and 25 to 42 lb at 30.0 and above. It gives no first-trimester figure, weekly rate or range for a single week, so the page shows the total and does not compare a weight for twins.
The IOM report says too little information was available to develop even a provisional guideline for underweight women with twins. The CDC page lists 50 to 62 lb and notes that this one figure is not from the IOM, so this page shows it only as a labelled CDC figure.
The IOM committee did not find enough evidence to change its guidelines for adolescents under 20 or for women of short stature, and it noted that younger adolescents often need to gain more. The guidelines are meant for women in the United States. A midwife or doctor can say which range applies to you.
The IOM prints the pound and kilogram ranges as separate columns, each rounded on its own. For example 25 lb is 11.3 kg, while the IOM prints 11.5 kg. This page uses each column as printed and does not convert one into the other.
No. It gives no diet, calorie or weight-loss advice and only shows the ranges the IOM and CDC publish. Questions about eating, exercise or weight in pregnancy are for a midwife, doctor or other qualified professional.
No. The calculation runs in your browser and nothing is sent to a server. The numbers go into the page address only after you change a value or tap Share link, and only your choice of metric or US units is remembered on your own device.