Crown Rump Length (CRL)

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Estimate gestational age using first trimester ultrasound measurements.

Ultrasound Measurement

Crown Rump Length

Pregnancy Dating

Gestational Age11weeks 0 days

ValidityValid range

Estimated Due Date (EDD)

March 21, 2027

About this calculator

Overview

Crown Rump Length (CRL) is the measurement of the length of human embryos and fetuses from the top of the head (crown) to the bottom of the buttocks (rump). It is the most accurate method for dating a pregnancy during the first trimester (approximately 6 to 14 weeks).

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Pro Tips

The fetus should be in a 'neutral' position (neither flexed nor extended) for the most accurate measurement.
Ensure the measurement is taken along the longest straight-line axis of the body.
If multiple measurements are taken, the longest one is usually used for dating.

Fun Facts

"CRL is accurate to within +/- 3 to 5 days for predicting the due date."
"Measurements are typically taken between 6 and 13 weeks + 6 days."
"An embryo's heart starts beating at a CRL of approximately 2-5 mm."
"After 14 weeks, measurements like Biparietal Diameter (BPD) become more accurate."

Formula: Gestational Age (Days) = CRL (mm) + 42 (Simplified) or Robinson's formula.