Slice thickness
Number of slices
Hemorrhage shape
Ellipsoid or round
ICH volume

ICH Volume Calculator

By Dominika Miszewska, PhD candidate
Last updated: Dec 09, 2020

This ICH volume calculator estimates the size of a parenchymal hemorrhage based on a CT scan (Computed Tomography scan). All you need to know are the dimensions of the bleed as determined by the scan. The tool applies the ABC2 (also known as ABC CT) formula.

What is the measure of ABC, and what exactly does this mysterious abbreviation stands for? Read the article below to get the answers. Also, we included an explanation of this ABC calculator's use with a practical example.

ABC CT medical abbreviation

ABC CT comes from a simplified formula which physicians use to estimate volume of a bleed. CT stands for computed tomography, the imaging method we use to estimate said volume. The ABC formula is as follows:

ICH volume = A * B * C * slices / 2,


  • A - maximum length;
  • B - width perpendicular to A on the same head CT slice;
  • C - width of one slice; and
  • slices - the number of slices with hemorrhage.

ABC2 formula

The proper ABC2 formula is more developed than the one above:

ICH volume = A * B * C * slices / hemorrhage shape

The hemorrhage shape can be either round/ellipsoid (and therefore equal to 2) or irregular/separated/multinodular (equal to 3).

Note, that the volume of an ellipsoid is 4/3 * π * (A/2) * (B/2) * (C/2). With a rough estimation of π ~3, the volume becomes A*B*C/2.

Parenchymal hemorrhage causes

A parenchymal hemorrhage, also known as intracerebral bleeding, may be caused by various chronic and acute conditions. Among the most common health issues that contribute greatly to the risk of hemorrhage is hypertension - elevated blood pressure may result in the tearing of arteries' walls inside the skull. To prevent this, keep your blood pressure below 120/80 mmHg.

What else may cause an ICH?

  • Drugs which influence the INR, such as heparin and warfarin used to prevent clots in heart and stroke conditions, may cause ICH. Also, alcohol, cocaine, and other illicit drugs;
  • Arteriovenous malformation;
  • An aneurysm;
  • Head trauma, fractures, penetrating wounds, car accidents, even if there is no open wound in the skull;
  • Bleeding disorders: hemophilia, sickle cell anemia, DIC, thrombocytopenia;
  • Tumors, such as angiomas and metastatic tumors, as they are highly vascularized;
  • Amyloid angiopathy; and
  • Nothing - bleeding may be spontaneous.

ABC calculator

To use this ICH volume calculator, all you need is some data, preferably data derived from a head CT scan.

  1. Measure the length (A) and width (B) of the bleeding.

  2. Count the number of CT scan slices with bleeding (C) and the approximate width of each slice. If the area of hemorrhage covers ≥75% of the slice, it counts as one slice. Similarly, if the area of bleeding is between 25 and 75%, it counts as 0.5 slices. Otherwise, the slice doesn't count.

You can choose how many slices of which type you have, and the number of slices is calculated automatically in the advanced mode.

  1. Finally, choose the hemorrhage's shape, whether it's ellipsoid, round, separated, multinodular, or irregular.

The formula to calculate ABC CT - based is simple:

ICH volume = A * B * C * slices / hemorrhage shape

For ellipsoid and round shapes, hemorrhage shape is substituted by 2. In the case of a separated, multinodular, or irregular shape, use 3 instead.

The result is the ICH volume in either ml, mm3 or cm3.

An intracerebral hemorrhage volume of >50-60 mL is a poor prognostic marker.

ICH volume calculator - a practical example

Let's work on an example. We have 65-year old Robert, admitted to the Neurology Department because he is having trouble moving his right side of the body after falling from a chair and knocking himself unconscious. The physicians, suspecting a stroke, decided to do a head CT scan and discovered a major parenchymal hemorrhage. How big? Well, that's what they're trying to figure out now with the ABC formula from this ICH volume calculator.

  • Length: 5 cm;
  • Width: 3 cm;
  • CT scan slice thickness: 2 mm;
  • Number of slices: 40; and
  • Shape: Ellipsoid.

ICH volume = 5 * 3 * 0.2 * 40 / 2

ICH volume = 60 mL3

This volume indicates a relatively poor outcome for the patient.

Dominika Miszewska, PhD candidate