ICH Volume Calculator — ABC/2 Hematoma Volume
Estimate intracerebral hemorrhage volume on CT with the ABC/2 method from the largest diameter, its perpendicular and the vertical depth or slice count, and check the 30 mL ICH score cut-off.
How it works
Volume (mL) = A × B × C ÷ 2 with A, B, C in cm. Slice method: C = (slices ≥ 75% × 1 + slices 25–75% × 0.5) × slice thickness (cm). ABC/2 approximates the ellipsoid volume 4/3 π (A/2)(B/2)(C/2) = ABC × π/6 by taking π ≈ 3.
The ABC/2 method (Kothari et al., Stroke 1996) estimates intracerebral hemorrhage volume at the bedside from a CT scan without planimetry software. A is the largest diameter on the slice with the biggest bleed, B is the largest diameter perpendicular to A on the same slice, and C is the vertical extent — either measured on coronal or sagittal images or estimated by counting slices, each weighted by how its area compares with the largest slice. Volume is a key predictor of outcome: 30 mL or more scores a point in the ICH score, and 60 mL or more with a GCS of 8 or less carried very high 30-day mortality in Broderick’s study. ABC/2 overestimates irregular or lobar hemorrhages.
Worked example
A hemorrhage measures A = 4 cm and B = 3 cm on its largest axial slice and extends C = 3 cm vertically: volume = 4 × 3 × 3 ÷ 2 = 18.0 mL — under 30 mL, so it adds 0 points to the ICH score. Counting slices gives the same C: (5 + 2 × 0.5) × 0.5 cm = 3 cm.
Sources: Kothari RU et al. The ABCs of measuring intracerebral hemorrhage volumes. Stroke 1996;27:1304–1305 · Hemphill JC et al. The ICH score: a simple, reliable grading scale for intracerebral hemorrhage. Stroke 2001;32:891–897
Frequently asked questions
How accurate is ABC/2?
For round or ellipsoid hematomas it is close to computer-assisted planimetry. It tends to overestimate irregular, lobar or anticoagulant-related bleeds; some studies suggest ABC/3 for very irregular shapes.
How do I measure C?
Either measure the vertical height on coronal or sagittal reconstructions, or count the axial slices with blood: slices with an area at least 75% of the largest count as 1, slices with 25–75% count as 0.5, and smaller ones are ignored; multiply by the slice thickness in cm.
Why does 30 mL matter?
In the ICH score, a hemorrhage volume of 30 mL or more adds 1 point, and larger volumes predict higher mortality and worse functional outcome.
Is the result in mL or cm³?
Both — 1 cm³ equals 1 mL. Enter all three diameters in centimeters.
Related calculators
Clinical decision tool for education and for use by trained clinicians alongside clinical judgement — not a diagnosis and not a substitute for medical assessment. Scores and cut-offs come from the cited validation studies and may not apply to every patient; follow local protocols.