Pregnancy Weight Gain Calculator · Practical guide
How Much Weight Should I Gain During Pregnancy?
Your pre-pregnancy BMI sets the target — the IOM ranges below are the standard US guidelines.
At a glance
The Short Answer
For a woman starting pregnancy at a normal weight (BMI 18.5–24.9), the Institute of Medicine recommends a total gain of 25 to 35 pounds. Lower starting weights call for more gain; higher starting weights call for less.
Interactive tool
Pregnancy Weight Gain Calculator
Enter your own values, then compare the result with the examples below.
Weight Gain Recommendations
The IOM Guidelines by BMI
| Pre-pregnancy BMI | Category | Total Gain | Weekly Gain (2nd/3rd Trimester) |
|---|---|---|---|
| Below 18.5 | Underweight | 28–40 lb | 1.0–1.5 lb |
| 18.5–24.9 | Normal weight | 25–35 lb | 0.5–1.0 lb |
| 25–29.9 | Overweight | 15–25 lb | 0.4–0.6 lb |
| 30 and above | Obese | 11–20 lb | 0.3–0.5 lb |
A Worked Example
A woman who is 5 feet 5 inches and weighed 140 pounds before pregnancy has a BMI of 23.3 — normal weight. Her recommended total gain is 25–35 lb, delivered at about 0.5–1 lb per week after the first trimester. The calculator above shows the same range plus the expected gain at her current week.
Where the Weight Actually Goes
Very little of the gain is body fat. A typical 30-pound gain at term breaks down roughly as: baby 7–8 lb, placenta about 1.5 lb, amniotic fluid 2 lb, breast tissue 2 lb, increased blood volume 4 lb, extra body fluids 4 lb, and maternal fat stores around 7 lb. That is why gaining far below the range — or trying to lose weight — is not considered safe during pregnancy.
Frequently Asked Questions
How much weight should I gain in the first trimester?
Only about 1–5 pounds total, regardless of BMI category. Steady gain at your category's weekly rate begins in the second trimester.
What if I am carrying twins?
The IOM recommends higher ranges for twins — for example, 37–54 lb for normal-weight mothers. The calculator above is calibrated for singleton pregnancies, so ask your provider for twin targets.
Is it safe to lose weight while pregnant?
Intentional weight loss is generally not recommended during pregnancy, even for women with obesity. Your provider can help you aim for the low end of your recommended range instead.
I am gaining faster than the guideline — what should I do?
Talk to your healthcare provider before changing your diet. They can review nutrition and activity to keep you on track without restricting what the baby needs.