Crown-Rump Length (CRL)
Growth Chart & Percentile Calculator
Compare your ultrasound measurement against standard first-trimester clinical growth curves. Check if your baby is within the 5th, 50th (median), and 95th percentiles.
Ultrasound Scan Lookup
Check if fetal CRL is on track for gestational age
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Measured: 24.0 mm (Normal: 22.5 – 29.5 mm)
Your measurement is within the healthy, expected range for this gestational age. Most healthy embryos track closely along the 50th percentile median.
Normal CRL Ultrasound Growth Chart (6 to 14 Weeks)
Standard obstetric reference values for crown-rump length across first-trimester development according to Robinson & Fleming (BMUS criteria).
| Gestational Age | 5th Percentile | 50th Percentile (Median) | 95th Percentile |
|---|---|---|---|
| 6w 0d | 3.5 mm | 5.0 mm (0.50 cm) | 7.2 mm |
| 7w 0d | 8.2 mm | 10.0 mm (1.00 cm) | 12.8 mm |
| 8w 0d | 14.2 mm | 16.5 mm (1.65 cm) | 19.8 mm |
| 9w 0d | 21.3 mm | 24.2 mm (2.42 cm) | 28.1 mm |
| 10w 0d | 29.8 mm | 33.5 mm (3.35 cm) | 38.2 mm |
| 11w 0d | 40.1 mm | 44.8 mm (4.48 cm) | 50.4 mm |
| 12w 0d | 51.5 mm | 57.2 mm (5.72 cm) | 64.0 mm |
| 13w 0d | 63.8 mm | 70.5 mm (7.05 cm) | 78.5 mm |
| 13w 6d | 74.0 mm | 84.0 mm (8.40 cm) | 92.0 mm |
Clinical Guide: What Do CRL Percentiles Mean?
Understanding statistical percentiles and why early ultrasound variation is usually benign.
! What if my baby's CRL is below the 5th percentile?
In over 90% of cases, an embryonic CRL that measures below the 5th percentile simply reflects delayed ovulation or late implantation. Menstrual dating assumes ovulation occurred exactly on Day 14 of a 28-day cycle; in reality, ovulating on Day 20 or 22 means the embryo is physically younger than calendar dates suggest. As long as cardiac activity is normal (110–160 bpm), obstetricians typically schedule a follow-up interval ultrasound in 10 to 14 days to confirm appropriate growth velocity.
↑ What if CRL is above the 95th percentile?
An embryo measuring larger than the 95th percentile usually indicates earlier-than-expected conception or vigorous early somatic development. When CRL exceeds LMP dates by more than 5 to 7 days, ACOG guidelines recommend moving the official Estimated Due Date earlier to avoid post-term complications.
✓ Why CRL is not used after 14 weeks (84 mm)
Once an embryo reaches 84 mm (~13 weeks and 6 days), spinal flexion, limb stretching, and active fetal movement cause straight-line crown-rump length to lose accuracy. Beyond 14 weeks, sonographers transition to multi-parametric fetal biometry: Biparietal Diameter (BPD), Head Circumference (HC), Abdominal Circumference (AC), and Femur Length (FL).