Pregnancy Weight Gain Calculator
IOM total and mid-pregnancy expected gain bands from pre-pregnancy BMI. Click any i for detail.
Weight & weeks
Pre-pregnancy weight (lb)
i
Pre
Weight before pregnancy. |
|
|---|---|
Height (in)
i
Height
For BMI category. |
|
Current weight (lb)
i
Now
Today’s weight. |
|
Gestational weeks
i
Weeks
Completed weeks. |
How to use this calculator
- Enter pre-pregnancy weight and height.
- Enter current weight and gestational weeks.
- Read BMI category, gain so far, and IOM total range.
- Follow your prenatal team’s personalized targets.
Results explained
IOM singleton guidelines set total gain ranges by pre-pregnancy BMI category, with slower first-trimester gain and steadier weekly rates afterward. Twins, adolescents, and medical conditions need different plans.
Quick reference: IOM total gain (singleton)
Underweight 28–40 lb; normal 25–35; overweight 15–25; obese 11–20.
| Item | Detail |
|---|---|
| BMI <18.5 | 28–40 lb total |
| 18.5–24.9 | 25–35 lb |
| 25–29.9 | 15–25 lb |
| ≥30 | 11–20 lb |
Educational IOM sketch — not individualized medical advice.
How the estimate is built
BMI = 703×lb/in²; compare gain to IOM band; mid expect ≈ early + weekly×max(0, weeks−13).
Example scenario
140 lb, 64 in, now 155 at 20 weeks → normal BMI, gain 15 lb vs ~25–35 lb total target.
FAQ
Twins?
Higher IOM ranges — not selected on this page.
Metric units?
Convert to lb/in first, or use a converter.
First trimester little gain?
Common; the model uses a small early allowance.
Obese category weekly rates?
Lower weekly targets — shown in the breakdown.