Pregnancy Weight Gain Calculator
See the recommended weight gain for your pre-pregnancy BMI, by week.
Runs in your browser — nothing is sent or saved.
How to use the pregnancy weight gain calculator
- Pick metric or imperial.
- Enter your pre-pregnancy weight and your height.
- Add your current week, and current weight, to see where you sit.
- Read the recommended total gain for your pre-pregnancy BMI.
How much weight to gain during pregnancy
Healthy pregnancy weight gain depends on your pre-pregnancy body mass index, so this tool first works out your BMI from your pre-pregnancy weight and height, then shows the range for that category, including the expected weight gain by trimester. The lower your starting BMI, the more gain is generally suggested, and the higher it is, the less. These are the widely used ranges for carrying a single baby.
The IOM weight gain ranges
| Pre-pregnancy BMI | Total gain |
|---|---|
| Underweight (under 18.5) | 12.5 to 18 kg (28 to 40 lb) |
| Healthy weight (18.5 to 24.9) | 11.5 to 16 kg (25 to 35 lb) |
| Overweight (25 to 29.9) | 7 to 11.5 kg (15 to 25 lb) |
| Obese (30 and over) | 5 to 9 kg (11 to 20 lb) |
Source: Institute of Medicine and National Research Council (now the National Academies of Sciences, Engineering, and Medicine), Weight Gain During Pregnancy: Reexamining the Guidelines (2009). These figures are for a single baby; a twin pregnancy uses different, higher ranges.
Gain by trimester
Most of the gain comes in the second and third trimesters. The first trimester usually adds only a small amount, often around 0.5 to 2 kg (1 to 4 pounds). After that, a steady weekly gain makes up most of the total, and the healthy weekly rate is higher for those who started at a lower BMI. The tool estimates the expected range at the week you enter so you can see whether you are on track.
An estimate, not medical advice
These are general population guidelines, not a personal target. The right amount for you depends on your health, your baby, and your pregnancy, and only your doctor or midwife can set it. Do not try to diet or restrict weight gain in pregnancy on your own. This is not medical advice.
FAQ
How much weight should I gain during pregnancy?
It depends on your pre-pregnancy BMI. A healthy-weight person carrying one baby is generally guided toward 11.5 to 16 kg (25 to 35 lb) in total. Enter your details to see your range.
Does pre-pregnancy weight change the recommendation?
Yes. The ranges are set by pre-pregnancy BMI: more gain is suggested for those who started underweight and less for those who started overweight or obese.
How much of the gain is in the first trimester?
Usually only a small amount, often about 0.5 to 2 kg (1 to 4 pounds). Most of the gain happens steadily through the second and third trimesters.
Are these ranges for twins?
No. These are for a single baby. Twin and multiple pregnancies have different, higher ranges, so follow your care team's guidance.
Is my information private?
Yes. Everything is calculated in your browser and nothing you enter is uploaded or saved.