Crown Rump Length Chart: Fetal Ultrasound Measurements

What is the fetal crown-rump length?

The fetal crown-rump length (CRL) is defined as the longest length of the fetus excluding the limbs and yolk sac. It is the measurement between the top of the head to the area above where the legs begin.

The fetal crown-rump length is taken via ultrasound usually up to the 14th week of the pregnancy.

This chart shows approximate crown-rump lengths according to days of fertilization and the last menstrual period.

Check out our comprehensive ultrasound guide!

Days (LMP)	Days (Fertilization)	(weeks/days)	(mm)
37	23	5.2	1
38	24	5.3	2
39	25	5.4	3
40	26	5.5	3
41	27	5.6	4
42	28	6	4
43	29	6.1	5
44	30	6.2	6
45	31	6.3	7
46	32	6.4	8
47	33	6.5	9
48	34	6.6	10
49	35	7	11
50	36	7.1	11
51	37	7.2	12
52	38	7.3	12
53	39	7.4	13
54	40	7.5	14
55	41	7.6	15
56	42	8	17
57	43	8.1	18
58	44	8.2	19
59	45	8.3	20
60	46	8.4	21
61	47	8.5	22
62	48	8.6	22
63	49	9	23
64	50	9.1	24
65	51	9.2	26
66	52	9.3	27
67	53	9.4	28
68	54	9.5	29
69	55	9.6	31
70	56	10	34
71	57	10.1	36
72	58	10.2	37
73	59	10.3	38
74	60	10.4	39
75	61	10.5	39
76	62	10.6	40
77	63	11	44
78	64	11.1	45
79	65	11.2	47
80	66	11.3	48
81	67	11.4	52
82	68	11.5	55
83	69	11.6	56
84	70	12	57
85	71	12.1	58
86	72	12.2	60
87	73	12.3	61
88	74	12.4	63
89	75	12.5	64
90	76	12.6	65
91	77	13	68
92	78	13.1	70
93	79	13.2	72
94	80	13.3	74
95	81	13.4	76
96	82	13.5	77
97	83	13.6	80
98	84	14	81
99	85	14.1	84
100	86	14.2	85
101	87	14.3	86
102	88	14.4	87

CRL

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sonogram

Ultrasound Measurements

crown rump length (CRL)