ICH Volume Calculator — ABC/2 Method for Intracerebral Hemorrhage
Estimate the volume of an intracerebral hemorrhage (ICH) directly from CT scan measurements using the ABC/2 method. Enter the two largest axial diameters, the number of slices and the slice thickness to get the hemorrhage volume in mL — an input required for the ICH Score and other clinical decision tools.
cm
cm
cm
Validated clinical estimate; volume ≥ 30 mL is associated with higher ICH Score risk
17.5 mL
- 1
Hemorrhage height C = slices × thickness
5 × 0.5 cm = 2.5 - 2
Product A × B × C
4 × 3.5 × 2.5 = 35 - 3
Volume = A × B × C ÷ 2
35 ÷ 2 = 17.5Dividing by 2 approximates the ellipsoid formula πABC/6 with <5% underestimation.
How does this calculator work?
ICH volume ≈ A × B × C / 2 (in mL), where A and B are the two largest perpendicular diameters on the widest axial CT slice and C = number of slices with blood × slice thickness in cm. The formula approximates the ellipsoid equation πABC/6 with <5% underestimation. Volume ≥ 30 mL is a key threshold in the ICH Score.
Formula
How this is calculated
The ABC/2 method was validated by Broderick et al. (1996, STROKE) as a rapid, reliable bedside approximation of hemorrhage volume on non-contrast CT. A is the largest diameter of the hemorrhage on any single axial slice; B is the largest diameter perpendicular to A on the same slice; C is the total hemorrhage height, calculated as the number of CT slices showing any blood multiplied by the slice thickness. Volume = A × B × C / 2 gives the result in cm³ (= mL) since CT measurements are in centimetres.
The formula approximates the exact ellipsoid volume πABC/6 (≈ 0.524 × ABC) but uses 0.5 × ABC instead, yielding a slight conservative underestimate of about 4.6%. This is clinically acceptable given the inherent uncertainty in CT-based measurements, and the simplicity of ABC/2 makes it practical at the bedside or in the emergency department without a calculator.
A volume ≥ 30 mL is one of the five variables in the validated ICH Score and carries a 1-point penalty for mortality risk. Volumes below 10 mL are generally associated with better outcomes, though location and patient factors matter equally. The ABC/2 method is not validated for non-ellipsoidal hemorrhages (e.g., very irregular, septated, or ventricular blood only).
Frequently asked questions
The ABC/2 method estimates hemorrhage volume from three CT measurements. Independent studies show it correlates closely (r > 0.95) with volumetric planimetry — the gold standard — for most supratentorial hemorrhages. Accuracy decreases for irregular or multilobar bleeds; in those cases, dedicated volumetric software is preferred.
On the axial slice where the hemorrhage appears largest, measure A as the longest diameter. Measure B as the widest diameter perpendicular to A on the same slice. For C, scroll through all CT slices and count every slice showing hemorrhage; multiply that count by the slice thickness (in cm). For 5 mm slices, use 0.5 cm per slice.
A volume of ≥ 30 mL earns 1 point in the ICH Score (Hemphill 2001), and volumes above 60 mL are associated with very high 30-day mortality. However, volume is only one factor — location, GCS, patient age and the presence of intraventricular blood all affect prognosis. Use the ICH Score calculator for a composite risk estimate.
TG we-Calculate Editorial Team. (2026). ICH Volume Calculator — ABC/2 Method for Intracerebral Hemorrhage [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/ich-volume-calculator
TG we-Calculate Editorial Team. "ICH Volume Calculator — ABC/2 Method for Intracerebral Hemorrhage." TG we-Calculate. 2026. https://we-calculate.com/calculator/ich-volume-calculator.
TG we-Calculate Editorial Team, "ICH Volume Calculator — ABC/2 Method for Intracerebral Hemorrhage," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/ich-volume-calculator
@misc{wecalculate_ich_volume_calculator, title = {ICH Volume Calculator — ABC/2 Method for Intracerebral Hemorrhage}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/ich-volume-calculator}}, year = {2026}, note = {TG we-Calculate} }
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