Fetal Weight Estimator
Estimate fetal weight by gestational week.
See average weight and length for each stage of pregnancy.
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Estimated Fetal Size
Fetal weight increases steadily throughout pregnancy, with the most rapid growth in the third trimester.
Average fetal weight by week:
| Week | Weight (g) | Weight (oz) | Length (cm) |
|---|---|---|---|
| 12 | 14 | 0.5 | 5.4 |
| 16 | 100 | 3.5 | 11.6 |
| 20 | 300 | 10.6 | 25.6 |
| 24 | 600 | 21.2 | 30.0 |
| 28 | 1,000 | 35.3 | 37.6 |
| 32 | 1,700 | 60.0 | 42.4 |
| 36 | 2,600 | 91.7 | 47.4 |
| 40 | 3,400 | 119.9 | 51.2 |
Note: These are averages. Individual babies vary significantly. Actual fetal weight is best assessed by ultrasound. Always consult your healthcare provider.