Pregnancy weight gain calculator
Recommended weight gain for your week of pregnancy and starting BMI, for one baby or twins.
- ๐บ๐ธ US federal & state rules
- Institute of Medicine pregnancy weight gain guidelines
- See sources
Recommended total gain
25 to 35 lb
Starting BMI 23.3, normal weight, one baby
- BMI before pregnancy
- 23.3 (normal weight)
- Gain by week 24
- 9.9 to 15.4 lb
- Weight at week 24
- 149.9 to 155.4 lb
- Gained so far
- 18 lb, 2.6 lb above the range
This is an example. Enter your numbers above and press the button to see your own result.
Recommended gain by week
| Week 12 | 1 to 4.1 lb (weight 141 to 144.1 lb) |
|---|---|
| Week 16 | 3.5 to 7.4 lb (weight 143.5 to 147.4 lb) |
| Week 20 | 6.7 to 11.4 lb (weight 146.7 to 151.4 lb) |
| Week 24 | 9.9 to 15.4 lb (weight 149.9 to 155.4 lb) |
| Week 28 | 13.1 to 19.4 lb (weight 153.1 to 159.4 lb) |
| Week 32 | 16.3 to 23.4 lb (weight 156.3 to 163.4 lb) |
| Week 36 | 19.5 to 27.4 lb (weight 159.5 to 167.4 lb) |
| Week 40 | 22.7 to 31.4 lb (weight 162.7 to 171.4 lb) |
- These are the 2009 Institute of Medicine (National Academies) ranges. They are general guidance, not medical advice. Set your own goal with your doctor or midwife.
Show the math
| BMI before pregnancy | 140 lb at 5 ft 5 in = 23.3 |
|---|---|
| BMI category | Normal weight (18.5 to 24.9) |
| Total gain at term (IOM) | 25 to 35 lb |
| First trimester (to week 13) | 1.1 to 4.4 lb |
| From week 14, per week | 0.8 to 1 lb ร 11 weeks |
| Total by week 24 | 9.9 to 15.4 lb |
What to do next
How it works
Your BMI before pregnancy sets the category: under 18.5, 18.5 to 24.9, 25 to 29.9, or 30 and over. Each category has a total gain range at term and a weekly rate for the second and third trimesters, from the 2009 Institute of Medicine report.
For a given week, the calculator spreads the first-trimester gain of 1.1 to 4.4 lb evenly over weeks 1 to 13, then adds the weekly rate for every week after that.
Things to keep in mind
This is not medical advice. The ranges are for adults; teens, twin pregnancies and people with health conditions may get different targets from their provider. The BMI cutoffs are the same for every ethnicity in the IOM report.
Sources
Rules applied as of 2009-05-28. See the sources below for details.
- IOM and NRC (2009), Weight Gain During Pregnancy, Summary Table S-1Checked 2026-10-19
Frequently asked questions
How much weight should I gain during pregnancy?
It depends on your BMI before pregnancy. The IOM range is 25 to 35 lb for a normal BMI, 28 to 40 lb if underweight, 15 to 25 lb if overweight and 11 to 20 lb with obesity.
How much weight should I gain in the first trimester?
The IOM guidance assumes about 1.1 to 4.4 lb (0.5 to 2 kg) in the first 13 weeks. After that, a normal-BMI pregnancy averages about 1 lb a week.
What about twins?
The IOM gives provisional totals at term: 37 to 54 lb for a normal BMI, 31 to 50 lb if overweight and 25 to 42 lb with obesity. It set no range for underweight twin pregnancies.
Is gaining outside the range dangerous?
Gaining much more or less than the range is linked to higher risks for mother and baby, but one number does not tell the whole story. Talk to your provider about your own target.