Crown-Rump Length (CRL)

Definition - What does Crown-Rump Length (CRL) mean?

Crown-rump length (CRL) is a measurement of an embryo or early fetus from the head (crown) to the bottom if its torso (rump). This is generally the longest length excluding limbs or the yolk sac.

CRL measurement is determined by ultrasound between 6 and 13 weeks and is considered to be the main reference for determining gestational age (GA) in early pregnancy as there is little variation at this point in development.

FertilitySmarts explains Crown-Rump Length (CRL)

The use of last menstrual period (LMP) is not always a practical assessment of gestational age for those who:

  • Have irregular menstrual cycles
  • Are uncertain of LMP
  • Conceived within 3 months of a previous pregnancy
  • Recently stopped taking oral contraceptives

Even in women who have regular 28-day cycles, there can be discrepancy in gestation age due to variations in the day of ovulation.

Crown-Rump Length Dating Table

There are multiple scales used to determine CRL. The scale below provides an idea of how a CRL measurement can be used to determine gestational age down to the week and day. Source: Loughna et al.


Gestational Age (Week + Day)
Crown-Rump Length (MM) 50th 5th 90th
5 6 + 0 5 + 2 6 + 5
6 6 + 2 5 + 4 7 + 0
7 6 + 3 5 + 6 7 + 1
8 6 + 5 6 + 0 7 + 2
9 6 + 6 6 + 2 7 + 4
10 7 + 1 6 + 3 7 + 5
11 7 + 2 6 + 4 8 + 0
12 7 + 3 6 + 5 8 + 1
13 7 + 4 7 + 0 8 + 2
14 7 + 5 7 + 1 8 + 3
15 7 + 6 7 + 2 8 + 4
16 8 + 1 7 + 3 8 + 5
17 8 + 2 7 + 4 8 + 6
18 8 + 3 7 + 5 9 + 0
19 8 + 3 7 + 6 9 + 1
20 8 + 4 8 + 0 9 + 2
21 8 + 5 8 + 1 9 + 3
22 8 + 6 8 + 1 9 + 4
23 9 + 0 8 + 2 9 + 5
24 9 + 1 8 + 3 9 + 6
25 9 + 2 8 + 4 9 + 6
26 9 + 3 8 + 5 10 + 0
27 9 + 3 8 + 6 10 + 1
28 9 + 4 8 + 6 10 + 2
29 9 + 5 9 + 0 10 + 3
30 9 + 6 9 + 1 10 + 3
31 9 + 6 9 + 2 10 + 4
32 10 + 0 9 + 2 10 + 5
33 10 + 1 9 + 3 10 + 6
34 10 + 2 9 + 4 10 + 6
35 10 + 2 9 + 5 11 + 0
36 10 + 3 9 + 5 11 + 1
37 10 + 4 9 + 6 11 + 1
38 10 + 4 10 + 0 11 + 2
39 10 + 5 10 + 0 11 + 3
40 10 + 6 10 + 1 11 + 3
41 10 + 6 10 + 2 11 + 4
42 11 + 0 10 + 2 11 + 5
43 11 + 0 10 + 3 11 + 5
44 11 + 1 10 + 3 11 + 6
45 11 + 2 10 + 4 11 + 6
46 11 + 2 10 + 5 12 + 0
47 11 + 3 10 + 5 12 + 1
48 11 + 4 10 + 6 12 + 1
49 11 + 4 10 + 6 12 + 2
50 11 + 5 11 + 0 12 + 2
51 11 + 5 11 + 1 12 + 3
52 11 + 6 11 + 1 12 + 4
53 11 + 6 11 + 2 12 + 4
54 12 + 0 11 + 2 12 + 5
55 12 + 1 11 + 3 12 + 5
56 12 + 1 11 + 3 12 + 6
57 12 + 2 11 + 4 12 + 6
58 12 + 2 11 + 4 13 + 0
59 12 + 3 11 + 5 13 + 0
60 12 + 3 11 + 6 13 + 1
61 12 + 4 11 + 6 13 + 1
62 12 + 4 12 + 0 13 + 2
63 12 + 5 12 + 0 13 + 3
64 12 + 5 12 + 1 13 + 3
65 12 + 6 12 + 1 13 + 4
66 12 + 6 12 + 2 13 + 4
67 13 + 0 12 + 2 13 + 5
68 13 + 0 12 + 3 13 + 5
69 13 + 1 12 + 3 13 + 6
70 13 + 1 12 + 4 13 + 6
71 13 + 2 12 + 4 14 + 0
72 13 + 2 12 + 5 14 + 0
73 13 + 3 12 + 5 14 + 0
74 13 + 3 12 + 6 14 + 1
75 13 + 4 12 + 6 14 + 1
76 13 + 4 13 + 0 14 + 2
77 13 + 5 13 + 0 14 + 2
78 13 + 5 13 + 0 14 + 3
79 13 + 6 13 + 1 14 + 3
80 13 + 6 13 + 1 14 + 4


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