Pregnancy Weight Gain
See your recommended total pregnancy weight gain based on your pre-pregnancy BMI, using the Institute of Medicine (IOM 2009) guidelines, plus where your current weight sits against a healthy gain range for your week. Includes a twin-pregnancy option.
How to Use
- Enter your pre-pregnancy weight in pounds — this sets your starting BMI category.
- Enter your height in inches so the calculator can work out your pre-pregnancy BMI.
- Enter how many weeks pregnant you currently are.
- Enter your current weight in pounds to see how your gain so far compares with the recommended range.
- Tick the Twins box if you are carrying twins to apply the higher recommended gain range.
Show Work
IOM 2009 ranges (lb)
About the Pregnancy Weight Gain
Whether you are at a desk or on your phone, the Pregnancy Weight Gain makes health and fitness tracking easy — and it is completely free. See your recommended total pregnancy weight gain based on your pre-pregnancy BMI, using the Institute of Medicine (IOM 2009) guidelines, plus where your current weight sits against a healthy gain range for your week. Includes a twin-pregnancy option.
How it works
Type your numbers into the boxes. The answer shows up right away — you do not have to press a button. If you change a number, the answer changes too. So you can try different numbers and watch what happens, or check an answer you worked out yourself. Just make sure each box has the right kind of number in it.
Want the deeper story? The Knowledge Base explains the ideas behind the tools in more detail.
Frequently Asked Questions
How much weight should I gain during pregnancy?
The IOM 2009 guidelines base total recommended gain on your pre-pregnancy BMI: about 28–40 lb if you were underweight (BMI under 18.5), 25–35 lb at a normal BMI (18.5–24.9), 15–25 lb if overweight (25–29.9), and 11–20 lb if obese (BMI 30 or above). Carrying twins raises these ranges. The calculator picks your range from the BMI it computes.
Where does the weight actually go?
Only a portion of pregnancy weight is the baby. A typical breakdown includes the baby itself (around 7–8 lb), the placenta, amniotic fluid, increased blood and fluid volume, larger breasts and uterus, and some maternal fat stores that support breastfeeding. This is why a healthy gain is considerably more than the baby's birth weight.
Is gaining outside the recommended range a problem?
Gaining well below or above the guideline range has been linked to higher risks for both mother and baby, but the guidelines are population-based ranges, not strict cutoffs. Your individual situation — including starting health, multiples, and any conditions — matters. Pace also counts: most gain happens in the second and third trimesters.
Does the recommendation change for twins?
Yes. Twin pregnancies generally call for more total weight gain than a single pregnancy. The IOM suggests higher ranges for twins (for example roughly 37–54 lb at a normal pre-pregnancy BMI), which is why this calculator adds to the range when you select the Twins option. Triplets and higher-order multiples need individualized guidance.
Should I rely on this calculator?
Use it as an educational reference only — it is not medical advice. Recommended pregnancy weight gain is a clinical matter that depends on your full health picture, and your obstetrician or midwife will track your gain at prenatal visits. Always follow the guidance of your own healthcare provider over a general calculator.
How do I use the Pregnancy Weight Gain?
Simply type your numbers and read the result, which refreshes the instant you change something. There is nothing to submit and nothing to wait for.
Is it free? Does it work without internet?
Yes to both. It is free with no sign-up, and once the page has loaded it keeps working even with no internet.
Where does my data go?
Nowhere — every calculation runs on your own device. Nothing you enter is uploaded, logged, or stored.
Common Use Cases
Setting a healthy gain target
Find your recommended total weight gain range based on your starting BMI.
Checking progress mid-pregnancy
Compare your current weight at a given week against the expected range.
Planning for twins
See the adjusted gain range that applies when carrying twins.
Preparing for a prenatal visit
Review your numbers before an appointment so you can discuss gain with your provider.
Understanding the guidelines
Learn how pre-pregnancy BMI maps to the IOM 2009 recommended weight-gain ranges.
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