Baby size can be estimated between 14 and 40 weeks of gestation and has an informative and playful character for future mothers. From a clinical point of view, your doctor will use the estimated fetal weight and long bones length to determine whether fetal growth is adequate or not.


Fetal length calculator is a tool that can help you estimate the length of your baby. The fetal length is the measurement of the fetus from head to toe. This can be helpful in understanding how big your baby is and what to expect during pregnancy. To use this calculator, simply enter the weight of the fetus and click calculate. The results will show the estimated fetal length. Keep in mind that this is only an estimate and your actual fetal length may vary.

Much ultrasound reports provide in the result only the estimated weight of the fetus. This happens because to evaluate the “size” of the baby the doctor uses the weight. If you have any questions, be sure to ask your doctor.

How do I calculate the fetal lenght

If your exam shows the fetal weight, don’t worry. It is possible to calculate the fetal length with our calculator. Just enter the fetal femur leght (in milimiters) and click on “Calculate”. The result will show you the estimated fetal length.

The fetal length formula

The fetal lenght formula is: Fetal Length = 6.18 + 0.59 x Femur Length in Millimeters. This formula was published in the literature and it’s based on a research.