Pregnancy Weight Gain Calculator
Enter your height and your weight before pregnancy. Add your week and current weight to compare your gain so far.
This is an estimate for general information and is not medical advice. There is no single right figure. Your midwife or doctor will look at your own situation.
Worked examples
Healthy weight, week 28
BMI 23.9, week 28, one baby
Expected gain so far about 5.8 to 9.5 kg
0.5 + 15 x 0.35 and 2 + 15 x 0.50.
About Pregnancy Weight Gain Calculator
Weight gain in pregnancy varies a great deal, and there is no single right figure. The Institute of Medicine in the United States published ranges in 2009 based on a woman’s BMI before pregnancy, and these are the most widely quoted. For one baby, the total is 12.5 to 18 kg (28 to 40 lb) if underweight, 11.5 to 16 kg (25 to 35 lb) at a healthy weight, 7 to 11.5 kg (15 to 25 lb) if overweight and 5 to 9 kg (11 to 20 lb) if obese.
This calculator works out your BMI from your height and weight before pregnancy, shows the range for your group and, if you add your week and current weight, compares your gain so far with where it is expected to be. Twin totals are provisional ones from the same report. NHS advice is that most women gain about 10 to 12.5 kg, and your midwife looks at your own situation. This is an estimate and not medical advice.
How to use Pregnancy Weight Gain Calculator
- Choose metric or imperial units.
- Enter your height and your weight before pregnancy.
- Say whether you are expecting one baby or twins.
- Add your week and current weight to see your gain so far against the range.
Common uses
- Understanding the published ranges before an appointment
- Seeing how gain is spread over the weeks
- Comparing singleton and twin ranges
- Tracking gain so far
Frequently asked questions
How much weight should I gain in pregnancy?
It depends on your BMI before pregnancy and whether you are carrying one baby or twins. For one baby the Institute of Medicine range is 11.5 to 16 kg (25 to 35 lb) at a healthy weight. The NHS says most women gain about 10 to 12.5 kg.
How much do I gain each week?
In the first 13 weeks, gain is usually 0.5 to 2 kg in total. After that, for a healthy weight, the range is about 0.35 to 0.5 kg (0.8 to 1 lb) a week. It is lower for those who start overweight and higher for those underweight.
Where do these ranges come from?
From the US Institute of Medicine report Weight Gain During Pregnancy (2009). They are based on studies of outcomes for mothers and babies, and are not UK rules.
What if I am outside the range?
Many healthy pregnancies fall outside the ranges. Talk to your midwife or doctor, who can look at your own health and growth scans. Do not try to diet in pregnancy unless advised.
Is this medical advice?
No. It is an estimate and not medical advice. Your midwife or doctor can advise you about your pregnancy.