Use this free online pregnancy weight gain calculator to find your pre-pregnancy BMI and the recommended total weight gain range for a healthy pregnancy. Just enter your pre-pregnancy height and weight to get an instant, guideline-based estimate. This tool offers general information only and is not a substitute for advice from your doctor or midwife.
General guideline — consult your doctor for personalized advice.
How to Use the Pregnancy Weight Gain Calculator
Enter your pre-pregnancy height in centimeters in the "Pre-Pregnancy Height (cm)" field.
Enter your pre-pregnancy weight in kilograms in the "Pre-Pregnancy Weight (kg)" field.
Click "Calculate Weight Gain" to see your results.
Review your pre-pregnancy BMI, BMI category, and recommended total weight gain range in the result box.
Where the Recommended Ranges Come From
The calculator first works out your pre-pregnancy BMI as weight in kg ÷ (height in m)², shown to two decimal places. It then matches that BMI to the total weight gain ranges published by the US Institute of Medicine (now the National Academy of Medicine) in 2009. These ranges are for a single baby and are widely used by obstetricians around the world.
The ranges get smaller as BMI rises. A woman who starts underweight needs more reserves for herself and the baby, while one who starts with a higher BMI already has stored energy, and gaining too much raises the risk of gestational diabetes, high blood pressure and a difficult delivery.
Recommended Weight Gain by Pre-Pregnancy BMI (Single Baby)
Category
Pre-pregnancy BMI
Total gain
Typical gain per week, 2nd and 3rd trimester
Underweight
Below 18.5
12.5–18 kg
0.44–0.58 kg
Normal weight
18.5–24.9
11.5–16 kg
0.35–0.50 kg
Overweight
25–29.9
7–11.5 kg
0.23–0.33 kg
Obese
30 and above
5–9 kg
0.17–0.27 kg
Weight gain is usually small in the first trimester, often around 0.5 to 2 kg in total, and some women lose a little because of nausea. Most of the gain happens steadily from the fourth month onwards, which is what the weekly figures describe.
Worked Examples
A woman who was 158 cm tall and weighed 55 kg before pregnancy has a BMI of 55 ÷ (1.58 × 1.58) = 22.03. That is in the normal range, so the recommended total gain is 11.5 to 16 kg, meaning a weight of roughly 66.5 to 71 kg by the end of pregnancy.
At 160 cm and 72 kg, the BMI is 28.12, which falls in the overweight category. The recommended total gain is 7 to 11.5 kg, or about 0.23 to 0.33 kg a week in the second half of pregnancy.
Notes for Indian Women
Many Indian clinical guidelines use lower Asian BMI cut-offs for adults, treating a BMI of 23 to 24.9 as overweight and 25 or more as obese. The ranges in this calculator are based on the standard cut-offs (25 and 30). If your BMI is between 23 and 25, ask your doctor which target range suits you.
"Eating for two" overstates what is needed. ICMR-NIN guidance calls for only a modest increase in daily calories from the second trimester, with the focus on protein, iron, calcium and folate rather than extra sweets and fried snacks.
Low weight gain is as much a concern as high gain. Too little gain is linked with low birth weight, so tell your doctor if your weight is not rising at your antenatal check-ups.
Use your pre-pregnancy weight, not your weight at the first antenatal visit. If you do not know it, a weight recorded early in the first trimester is the closest substitute.
Where the Extra Weight Goes
Only part of the gain is the baby. The rest is the placenta, amniotic fluid, the enlarged uterus and breasts, a substantial increase in blood volume and body fluid, and some fat stored to support breastfeeding. This is why weight gain within the recommended range is healthy and expected, and why dieting to lose weight during pregnancy should only be done under medical supervision.
This calculator gives general guidance and is not a substitute for advice from your doctor or midwife, especially if you have diabetes, thyroid disease, high blood pressure or are carrying more than one baby.
Frequently Asked Questions
BMI is calculated using the standard formula: weight in kilograms divided by the square of your height in meters (weight (kg) ÷ height (m)²), based on the height and weight you enter before pregnancy.
Once your BMI is calculated, it's matched to a category: Underweight (below 18.5) suggests 12.5-18 kg, Normal weight (18.5-24.9) suggests 11.5-16 kg, Overweight (25-29.9) suggests 7-11.5 kg, and Obese (30 or above) suggests 5-9 kg of total pregnancy weight gain.
The ranges on this page are for a single baby. For twins, the same 2009 guidelines give provisional ranges of about 17 to 25 kg for normal BMI, 14 to 23 kg for overweight and 11 to 19 kg for obese women. There was not enough data to set a range for underweight women, so your doctor will advise you.
Not without medical advice. The lower recommended gain for higher BMIs already takes your stored reserves into account. Focus on balanced meals and regular gentle activity such as walking, and let your doctor decide whether any change to your target is needed.
A small difference is common and usually not a cause for concern. If you are well outside the range, or your weight changes suddenly, for example a rapid gain with swelling of the face or hands, speak to your doctor promptly, as it can be a sign of a problem that needs checking.