Last updated: March 2026
What Is the Pregnancy Weight Tracker?
The Pregnancy Weight Tracker helps expectant mothers monitor weight gain throughout their pregnancy using the Institute of Medicine (IOM) 2009 guidelines. These evidence-based recommendations are still the standard used by healthcare providers worldwide.
The tool calculates your pre-pregnancy BMI and uses it to determine a personalized recommended weight gain range. It then compares your actual weight gain against this range, showing you a visual chart and week-by-week status updates.
Weight gain during pregnancy is a normal and essential part of growing a healthy baby. The weight includes the baby, placenta, amniotic fluid, increased blood volume, breast tissue, and fat stores needed for breastfeeding. The recommended total gain varies by BMI category because starting weight affects how much additional gain is healthy.
How to Track Your Pregnancy Weight
Start by entering your height and pre-pregnancy weight to calculate your BMI. Then enter your current weight and pregnancy week. The tool instantly shows whether your weight gain is on track, below, or above the recommended range for your week.
For the most consistent tracking, weigh yourself at the same time each day — ideally first thing in the morning. Daily fluctuations of 2-4 pounds are completely normal and caused by water retention, meals, and other factors. The weekly trend matters far more than any single reading.
Use the Log This Week's Weight button to save each week's measurement. Over time, you'll build a personal weight curve on the chart that you can share with your healthcare provider. All data is stored locally in your browser — nothing is sent to any server.
The Trimester Summary section breaks down expected versus actual gain for each trimester. First trimester gain is typically minimal (1-4 lbs), with the majority of gain happening in the second and third trimesters at a steady rate.
Frequently Asked Questions
How much weight should I gain during pregnancy?
It depends on your pre-pregnancy BMI. The Institute of Medicine recommends 25-35 lbs for normal weight (BMI 18.5-24.9), 28-40 lbs for underweight (BMI <18.5), 15-25 lbs for overweight (BMI 25-29.9), and 11-20 lbs for obese (BMI 30+). For twins, add 10-15 lbs to these ranges.
When does most pregnancy weight gain happen?
Most weight gain occurs in the second and third trimesters. During the first trimester (weeks 1-12), you might gain only 1-4 lbs total. After that, steady gain of about 0.5-1 lb per week is typical, depending on your BMI category.
What if I'm gaining too much or too little weight?
Don't panic — the IOM ranges are guidelines, not strict rules. Small deviations are normal. However, consistently gaining well above or below the recommended range can increase certain pregnancy risks. Talk to your healthcare provider, who can give you personalized guidance based on your specific situation.
Is the weight gain recommendation different for twins?
Yes. The IOM recommends about 37-54 lbs for normal weight mothers carrying twins, 31-50 lbs for overweight, and 25-42 lbs for obese. This tool adds 10-15 lbs to the singleton ranges when the twins toggle is enabled.
Is my weight data saved?
Your weekly weight log is saved in your browser's local storage, so it persists between visits on the same device. No data is sent to any server — everything stays on your device. You can also export your data as CSV or JSON at any time.