Complete Guide: Healthy Pregnancy Weight Gain by BMI
A pregnancy weight gain calculator helps you understand whether your weight gain is tracking within the healthy range recommended for your pre-pregnancy body mass index (BMI). This free tool uses the widely referenced Institute of Medicine (IOM) guidelines to estimate your ideal total weight gain and weekly gain rate.
💡 Quick Summary
Your recommended total weight gain depends on your pre-pregnancy BMI category and whether you're carrying one baby or twins. Underweight mothers are generally advised to gain more; those in the obese category are advised to gain less.
IOM Recommended Weight Gain Ranges (Singleton Pregnancy)
| Pre-Pregnancy BMI | Category | Total Recommended Gain | 2nd/3rd Trimester Rate |
|---|---|---|---|
| Below 18.5 | Underweight | 28–40 lb | 1.0–1.3 lb/week |
| 18.5–24.9 | Normal weight | 25–35 lb | 0.8–1.0 lb/week |
| 25–29.9 | Overweight | 15–25 lb | 0.5–0.7 lb/week |
| 30 and above | Obese | 11–20 lb | 0.4–0.6 lb/week |
Twin pregnancies have their own, higher recommended ranges since two babies require more maternal weight gain. Our calculator automatically applies the correct table based on your selection.
Step-by-Step Instructions
- Enter your pre-pregnancy weight and height.
- Enter your current weight and current week of pregnancy.
- Select singleton or twin pregnancy.
- Click ⚡ Calculate My Weight Gain Range.
- Review your BMI category, recommended total gain, weekly rate, and where you should be by your current week.
Note: This tool provides general guidance based on published IOM recommendations and is not a substitute for advice from your OB-GYN or midwife, who can account for your individual health history.