Pregnancy Weight Tracker
Track your weight gain based on IOM/ACOG guidelines
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Range: 3–8 ft, 0–11 in
Weight range: 66–440 lbs
Weeks 1–42
Understanding Pregnancy Weight Gain
Gaining weight during pregnancy is healthy and expected — it supports your baby's growth, the placenta, extra blood and fluid, and energy stores for breastfeeding. How much to gain depends mostly on your pre-pregnancy body mass index (BMI). This tracker uses the Institute of Medicine (IOM) 2009 guidelines, which are endorsed by the American College of Obstetricians and Gynecologists (ACOG) and the CDC, to estimate a healthy range for your week of pregnancy.
How Much Weight Should You Gain by BMI?
The IOM gives a total weight-gain range for the whole pregnancy plus a weekly rate for the second and third trimesters. These figures are for singleton (one baby) pregnancies:
BMI is calculated as weight in kilograms divided by height in metres squared (kg/m²). The first trimester adds only a small amount — roughly 1–4.4 lb (0.5–2 kg) in total — after which steady weekly gain begins.
Worked Example
Suppose you weighed 140 lb before pregnancy and are 5'5" (165 cm) tall. Your BMI is about 23.3, which falls in the normal weight range, so your recommended total gain is 25–35 lb. By week 20 (just past the half-way point), a healthy cumulative gain would be roughly 7–12 lb: the ~1–4 lb from the first trimester plus several weeks at about 1 lb/week. The tracker compares your actual gain to this range and tells you whether you're on track, with a margin so a normal week-to-week wobble isn't flagged as a problem.
Twin Pregnancy Weight Gain
If you're carrying twins, the IOM recommends higher provisional ranges (there was not enough data to set an underweight-twin recommendation, so use the normal-weight figure and your provider's advice):
Where Does the Weight Go?
Very little of pregnancy weight is body fat. At term, a typical 25–35 lb gain is distributed roughly as: baby 6.5–9 lb, fat stores for breastfeeding 5.5–9 lb, blood volume 3–4 lb, body fluids 2–4 lb, amniotic fluid ~2 lb, uterus ~2 lb, breast tissue 1–2 lb and placenta 1–2 lb. Most of this is lost over the weeks and months after birth.
Weight Gain by Trimester
- First trimester (weeks 1–13): minimal gain, about 1–4.4 lb total. Some people lose a little weight from morning sickness, which is usually not a concern.
- Second trimester (weeks 14–27): steady weekly gain begins, around 0.5–1 lb per week for most.
- Third trimester (weeks 28–40): continued steady gain; the baby puts on the most weight, and gain often slows again in the final couple of weeks.
Frequently Asked Questions
How much weight should I gain during pregnancy?
It depends on your pre-pregnancy BMI. Under the IOM 2009 guidelines, a normal-weight woman (BMI 18.5–24.9) should gain about 25–35 lb (11.3–15.9 kg). Underweight women aim for 28–40 lb, overweight women 15–25 lb, and women with obesity 11–20 lb.
How much weight should I gain in the first trimester?
Only a little — roughly 1–4.4 lb (0.5–2 kg) in total over the first 13 weeks. Steady weekly gain typically begins in the second trimester.
How much weight should I gain each week in the second and third trimesters?
For a normal-weight woman, about 0.8–1 lb per week. Underweight women gain a bit faster (1–1.3 lb/week), while overweight women aim for 0.5–0.7 lb/week and women with obesity for 0.4–0.6 lb/week.
How much weight should I gain if I am having twins?
Twin pregnancies need more. The IOM provisional ranges are 37–54 lb for normal weight, 31–50 lb for overweight, and 25–42 lb for obese. There is no separate underweight-twin recommendation, so use the normal-weight range and your provider's advice.
Is it normal to lose weight in early pregnancy?
Some weight loss from morning sickness in the first trimester is common and usually not a concern. Discuss significant or ongoing weight loss with your healthcare provider.
What if I am gaining more or less than recommended?
A single reading varies day to day — the overall trend matters more. If your gain is consistently faster or slower than the recommended range, contact your healthcare provider, who can give personalized advice based on your full history.
Related Tools and Reading
- Due Date Calculator and Ovulation Calculator — work out your week of pregnancy and conception date
- Baby Budget Calculator — plan for the costs that come with a new baby
- Baby BMI Calculator and Growth Tracker — follow your baby's growth after birth on WHO charts
- Baby-Led Weaning and Family Meals and 7 Simple Habits for a Healthier Family Lifestyle
- Warning Signs of Depression in Parents — emotional wellbeing matters before and after birth
Methodology and Sources
Recommended ranges reproduce the IOM 2009 report and the bodies that endorse it. The tracker estimates your expected gain for a given week by adding a small first-trimester amount to a steady second/third trimester rate, scaled so the cumulative total matches the guideline range at term (week 40):
- Institute of Medicine & National Research Council (2009), “Weight Gain During Pregnancy: Reexamining the Guidelines” — the source of the BMI-based ranges and weekly rates.
- ACOG — Weight Gain During Pregnancy (patient FAQ).
- CDC — Weight Gain During Pregnancy.
These ranges are general guidance, not a personal target. Healthy pregnancies vary, and your numbers may differ if you have a health condition, are carrying multiples, started at a very high or low BMI, or had weight changes from nausea. This tool is not medical advice — your prenatal provider tracks your weight in context and is the right person to set your individual goal.