Pregnancy Weight Gain Calculator · Practical guide
Pregnancy Weight Gain Chart by BMI
Find your pre-pregnancy BMI row to see your recommended total gain and weekly rate.
At a glance
The IOM Chart
| Category | BMI Range | Total Gain | Weekly Gain (2nd/3rd) |
|---|---|---|---|
| Underweight | Below 18.5 | 28–40 lb | 1.0–1.5 lb |
| Normal weight | 18.5–24.9 | 25–35 lb | 0.5–1.0 lb |
| Overweight | 25–29.9 | 15–25 lb | 0.4–0.6 lb |
| Obese | 30 and above | 11–20 lb | 0.3–0.5 lb |
Interactive tool
Pregnancy Weight Gain Calculator
Enter your own values, then compare the result with the examples below.
Weight Gain Recommendations
How to Find Your Row
BMI uses your weight and height before pregnancy: divide weight in pounds by height in inches squared, then multiply by 703. A woman who is 5 feet 6 inches (66 in) and weighed 160 lb before pregnancy has a BMI of 160 × 703 ÷ 4,356 ≈ 25.8 — the overweight row, with a 15–25 lb target. The calculator computes your BMI and category automatically.
Why the Targets Shrink as BMI Rises
Lower-BMI mothers need more gain to support fetal growth and build reserves, while women who start pregnancy heavier already carry energy stores — and gaining within the lower range reduces risks like gestational diabetes, preeclampsia, and cesarean delivery. The ranges balance the baby's needs against those complication risks.
Where the Numbers Come From
The chart follows the Institute of Medicine's 2009 gestational weight gain guidelines, the standard reference used by US obstetric providers. They apply to singleton pregnancies; twin pregnancies have separate, higher ranges your provider can supply.
Frequently Asked Questions
Which BMI do I use — before or during pregnancy?
Always your pre-pregnancy BMI. Your current weight during pregnancy includes the gain itself, so it would misplace you on the chart.
My BMI is 24.9 versus 25 — does one point matter?
The boundary rows differ by 10 lb of target gain, but real bodies do not change at a decimal point. If you sit right on a line, ask your provider which target fits you best.
Does this chart apply to twins?
No. Twin pregnancies have their own IOM ranges — for example, 37–54 lb for normal-weight mothers. Use the chart only for singleton pregnancies.
What if I was dieting right before getting pregnant?
Use your weight when the pregnancy began, even if it was an unusual low. If you feel the number is unrepresentative, your provider can help set a sensible target.