Abdominal Circumference To Head Circumference Ratio Calculator

Enter the abdominal circumference and head circumference into the calculator to determine the ratio, or enter the ratio and one of the circumferences to find the missing value.

Medical note: Educational use only; not a diagnostic tool. Use measurements from a clinician (or values listed on an ultrasound/medical report). Interpretation depends on age/gestational age, measurement technique, and clinical reference ranges—please discuss results with an OB-GYN, pediatric clinician, or other qualified healthcare professional.

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Abdominal Circumference To Head Circumference Ratio Formula

The following formula is used to calculate the abdominal circumference to head circumference ratio.

R = \frac{AC}{HC}

Variables:

• R is the ratio of abdominal circumference to head circumference
• AC is the abdominal circumference (enter any supported unit; the calculator converts internally)
• HC is the head circumference (enter any supported unit; the calculator converts internally)

To calculate the ratio, divide the abdominal circumference by the head circumference.

What is the Abdominal Circumference To Head Circumference Ratio?

The abdominal circumference to head circumference ratio is simply abdominal circumference (AC) divided by head circumference (HC). AC and HC are measurements that may be recorded in clinical settings (for example, on a fetal ultrasound report or during a clinician exam). Healthcare professionals may consider these measurements alongside age/gestational-age reference ranges, growth charts, and other clinical findings; the ratio alone does not determine a diagnosis.

How to Calculate Abdominal Circumference To Head Circumference Ratio?

The following steps outline how to calculate the Abdominal Circumference To Head Circumference Ratio.

1. First, measure the abdominal circumference (AC).
2. Next, measure the head circumference (HC).
3. Finally, calculate the ratio using the formula R = AC / HC.
4. After inserting the values and calculating the result, check your answer with the calculator above.

Example Problem (math only; not clinical reference values): 

Use the following variables as an example problem to test your knowledge.

Abdominal Circumference (AC) = 30 cm

Head Circumference (HC) = 25 cm

Ratio (R) = 1.2