Fetal Weight Calculator

Estimate fetal weight by gestational age and review the assumptions and uncertainty behind the result.

Biparietal Diameter (cm)

Abdominal Circumference (cm)

Femur Length (cm)

About the Fetal Weight Calculator:

1. About Biparietal Diameter (BPD)
(1) The fetal weight calculator is based on B-ultrasound and color Doppler measurements. It uses a formula (BPD × AC × FL) to estimate fetal weight, displaying results in pounds and kilograms.
(2) During fetal development, the formula provides an estimate. Generally, the actual birth weight may differ from the predicted weight by ±10-15%.
2. About Occipitofrontal Diameter (OFD)
(1) OFD, also known as 'anteroposterior diameter,' measures the longest distance from the front to the back of the fetal head, from the 'nasal root of the forehead' to the 'external occipital protuberance.'
3. About Head Circumference (HC)
(1) Head circumference is the largest perimeter around the fetal head, measured from the front to the back.
(2) Typically, it is the circumference from the 'nasal root of the forehead' to the 'external occipital protuberance.'
4. About Femur Length (FL)
(1) With the mother lying on her back, the doctor measures from the lower edge of the pubic bone to the upper edge of the pubic symphysis to estimate fetal growth.
(2) After 20 weeks of pregnancy, gestational age usually corresponds to this distance.
5. About Abdominal Circumference (AC)
(1) The abdominal circumference is measured at the widest part of the abdomen. Due to individual differences, expectant mothers are advised to measure regularly at home.

Normal Fetal Ultrasound Parameters

Gestational Week	Biparietal Diameter (cm)	Abdominal Circumference (cm)	Femur Length (cm)
13	2.52±0.25	6.90±1.65	1.17±0.31
14	2.83±0.57	7.77±1.82	1.38±0.48
15	3.23±0.51	9.13±1.56	1.74±0.58
16	3.62±0.58	10.32±1.92	2.10±0.51
17	3.97±0.44	11.49±1.62	2.52±0.44
18	4.25±0.53	12.41±1.89	2.71±0.46
19	4.52±0.53	13.59±2.30	3.03±0.50
20	4.88±0.58	14.80±1.89	3.35±0.47
21	5.22±0.42	15.62±1.84	3.64±0.40
22	5.45±0.57	16.70±2.23	3.82±0.47
23	5.80±0.44	17.90±1.85	4.21±0.41
24	6.05±0.50	18.74±2.23	4.36±0.51
25	6.39±0.70	19.64±2.20	4.65±0.42
26	6.68±0.61	21.62±2.30	4.87±0.41
27	6.98±0.57	21.81±2.12	5.10±0.41
28	7.24±0.65	22.86±2.41	5.35±0.55
29	7.50±0.65	23.71±1.50	5.61±0.44
30	7.83±0.62	24.88±2.03	5.77±0.47
31	8.06±0.60	25.78±2.32	6.03±0.38
32	8.17±0.65	26.20±2.33	6.43±0.49
33	8.50±0.47	27.78±2.30	6.52±0.46
34	8.61±0.63	27.99±2.55	6.62±0.43
35	8.70±0.55	28.74±2.88	6.71±0.45
36	8.81±0.57	29.44±2.83	6.85±0.47
37	9.00±0.63	30.14±2.17	7.10±0.52
38	9.08±0.59	30.63±2.83	7.20±0.43
39	9.21±0.59	31.34±3.12	7.34±0.53
40	9.28±0.50	31.49±2.79	7.40±0.53

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