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Crown Rump Length (CRL) Calculator

Crown Rump Length (CRL) is the measurement from the top of the fetus’s head (crown) to the bottom of the buttocks (rump), typically taken between 6 to 13 weeks of pregnancy. This calculator estimates fetal length based on gestational age or helps assess gestational age based on CRL.

Fetal Length by Gestational Week Calculator

Input Fields
If enabled, the result will update automatically when you change any value.

Crown Rump Length Estimation Formula

Formula
$$\text{CRL (mm)} = 0.99 \times (\text{Gestational Age (days)} – 42)$$

This approximation is valid between 6 and 13 weeks of gestation. It helps estimate fetal development and is often used in early ultrasound evaluations.

The Crown Rump Length (CRL) is one of the most accurate ways to determine the gestational age of a pregnancy in the first trimester. Typically measured via ultrasound, CRL helps clinicians date a pregnancy and track fetal growth. This calculator allows you to input either the gestational age in weeks to estimate CRL in millimeters, or the CRL to estimate gestational age. It is commonly used between 6 and 13 weeks, where accuracy is highest.

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2 thoughts on “Crown Rump Length (CRL) Calculator

  1. Gajendran says:

    In six week pregnant my CRL value is 0.34cmis this normal or not

  2. Jyoti says:

    Hi I am 9 weeks 6 days pregnant and my babies crl is 39mm. Is it normal.