Baby Weight Estimator
Estimate fetal weight and length based on weeks of pregnancy.
The Baby Weight Estimator provides an approximate fetal weight and length based on gestational age in weeks. Fetal growth follows a predictable curve, though individual variation is significant.
Enter the number of weeks pregnant (8-42). The calculator uses a simplified growth curve to estimate weight in grams and pounds, plus crown-to-heel length in centimeters.
Typical milestones: 12 weeks ~14g, 20 weeks ~300g, 28 weeks ~1000g, 36 weeks ~2700g, 40 weeks ~3400g. Actual weight depends on genetics, nutrition, and other factors. Ultrasound measurements provide more accurate individual estimates.
Frequently Asked Questions
How accurate are these weight estimates?
These are population averages and can vary significantly. Ultrasound-based estimates are more accurate for individual babies but still have a margin of error of 10-15%.
What is a normal birth weight?
Normal full-term birth weight ranges from 2500g to 4000g (5.5 to 8.8 lbs). The average is about 3400g (7.5 lbs).
When does the baby gain the most weight?
The third trimester (weeks 28-40) sees the most rapid weight gain, about 200-250 grams per week. The baby roughly doubles its weight in the last 8 weeks.