Frontal-Occipital Horn Ratio (FOHR)
Frontal-occipital horn ratio: (frontal-horn + occipital-horn width) / (2 × biparietal diameter); >= 0.55 marks clinically significant ventriculomegaly.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Maximum frontal-horn width
- 38 mm
- Maximum occipital-horn width
- 42 mm
- Biparietal diameter
- 110 mm
Result: Frontal-occipital horn ratio 0.36 — within the normal reference (mean 0.37).
The tool opens with these values already filled in. Replace them with your own.
What the result means
- <= 0.37
- Within the normal reference (mean 0.37).
- 0.37-0.55
- Above the normal mean.
- >= 0.55
- Clinically significant ventriculomegaly. A ratio, not a diagnosis.
What you enter
- Maximum frontal-horn width
- Maximum occipital-horn width
- Biparietal diameter
How this is calculated
O’Hayon BB, Drake JM, Ossip MG, Tuli S, Clarke M. Frontal and occipital horn ratio: a linear estimate of ventricular size for multiple imaging modalities in pediatric hydrocephalus. Pediatr Neurosurg. 1998;29(5):245-249. (>= 0.55 threshold: Ambati R, et al. AJR Am J Roentgenol. 2019.) Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.