ICH Volume Calculator

Estimate intracerebral hemorrhage volume from CT measurements using the ABC/2 method (A x B x C / 2).

Quick Facts

Formula
Volume (mL) = A x B x C / 2
Kothari et al., 1996 - the standard bedside CT estimate for ICH volume.
Volume threshold
30 mL
Cutoff used for the volume component of the ICH Score (Hemphill et al., 2001).

Your Results

Calculated
ICH volume
-
ABC/2 estimate
Vertical extent (C)
-
Slices x slice thickness
Volume category
-
Small / moderate / large band
ICH Score volume points
-
0 or 1 point at the 30 mL cutoff

Ready

Enter the A and B diameters plus the slice count and thickness, then calculate.

About the ICH volume calculator

The ABC/2 method, described by Kothari and colleagues in 1996, is the standard bedside formula for estimating the volume of an intracerebral hemorrhage (ICH) from a non-contrast CT scan. It approximates the hematoma as an ellipsoid and multiplies three measured diameters, then divides by two. Despite its simplicity, ABC/2 correlates closely with volumes measured by computer-assisted planimetry and remains the most widely used method in stroke research and clinical practice.

How the measurements are taken

  • A is the largest hemorrhage diameter measured on the single CT slice that shows the biggest hemorrhage cross-sectional area.
  • B is the diameter perpendicular to A, measured on that same slice.
  • C approximates the vertical extent of the hematoma. The common bedside approximation multiplies the number of CT slices that show hemorrhage by the slice thickness (in cm) reported by the scanner.

The formula

Volume (mL) = A x B x C / 2. Because 1 cubic centimeter equals 1 milliliter, the result reads directly in mL. This calculator only performs that arithmetic — the diameters, slice count, and slice thickness must come from a CT image that has already been reviewed by a radiologist or clinician.

Putting the result in context

ICH volume is one of the strongest predictors of outcome after hemorrhagic stroke and is a component of validated severity indices such as the ICH Score, where a volume of 30 mL or more contributes a point. Volumes are commonly grouped as small (under about 30 mL), moderate (30 to 60 mL), and large (above 60 mL), but these bands describe statistical associations across patient groups, not a forecast for any one person.

When to consult a professional

This calculator performs the standard ABC/2 arithmetic for education and documentation. It is not a diagnosis and does not direct treatment. Any decision about monitoring, surgery, or care should rest with the treating clinical team, who interpret the volume alongside hemorrhage location, the patient's neurological exam, and imaging trends over time.

Frequently Asked Questions

What formula does this ICH volume calculator use?
It uses the ABC/2 method (Kothari et al., 1996), the standard bedside estimate for intracerebral hemorrhage volume on CT. Volume in mL equals A x B x C / 2, where A is the largest hemorrhage diameter on the CT slice with the biggest hemorrhage area, B is the diameter perpendicular to A on that same slice, and C is the hemorrhage's vertical extent, found by multiplying the number of CT slices that show hemorrhage by the slice thickness.
How do I measure A, B, and the slice count from a CT scan?
A radiologist or clinician identifies the axial CT slice with the largest hemorrhage area, measures its longest diameter as A, then measures the diameter perpendicular to A on that same slice as B. C is derived by counting how many contiguous slices show hemorrhage and multiplying by the slice thickness reported by the scanner. This calculator only performs the arithmetic; the measurements themselves must come from a reviewed CT image.
What do the volume categories mean?
Volumes under about 30 mL are generally considered small, 30 to 60 mL moderate, and above 60 mL large. A volume of 30 mL or more is also the threshold used for the volume component of the ICH Score (Hemphill et al., 2001), a widely used severity index. These bands describe population-level associations with outcome, not a diagnosis or prognosis for any individual, and should be interpreted by a clinician alongside the full clinical picture.

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