Introduction
An intracerebral hemorrhage (ICH) is bleeding inside the brain. The size of that bleed matters. A bigger bleed often means a worse outcome, so doctors need to know the volume fast.2 This ICH Volume Calculator works out that volume from three CT measurements.
The tool uses the ABC/2 formula, a trusted bedside method for measuring hematoma volume on a head CT scan.1 You enter three things:
- A is the longest width of the bleed on the CT slice where it looks biggest1
- B is the widest part that crosses A at a right angle, on that same slice1
- C is how tall the bleed is from top to bottom
You can type C in yourself, or let the calculator work it out from the number of CT slices and the slice thickness. If the bleed has an odd, split, or lumpy shape, switch to ABC/3 for a closer estimate.7
The result shows the volume in mL (cm³), an estimated range for measurement error, and the volume group it falls in. You also get a step-by-step breakdown of the math and report-ready text you can copy into your notes.
This calculator is a quick estimate tool for trained clinicians. It does not replace a full radiology read or your own clinical judgment.
How to use our ICH Volume Calculator
Enter the shape of the brain bleed and its three sizes from the CT scan. The tool gives you the hemorrhage volume in mL, an estimated range, a volume group, and report-ready text.
Hemorrhage Shape: Pick "Round / Ellipsoid" for a normal, smooth bleed. Pick "Irregular / Separated / Multinodular" for a bleed with an odd or broken-up shape. This sets the formula to ABC/2 or ABC/3.
Input Unit System: Choose cm or mm for your measurements. If you switch, all your numbers change over for you.
Hemorrhage Length (A): Type the longest width of the bleed. Measure it on the CT slice where the bleed looks biggest.
Hemorrhage Width (B): Type the longest width that crosses A at a right angle. Use the same CT slice you used for A.
Craniocaudal entry method: Pick "Direct measurement" if you measured the height of the bleed yourself. Pick "Calculate via CT slices" to let the tool work out the height from your slice count.
Craniocaudal Dimension (C): If you chose direct, type the top-to-bottom height of the bleed from the coronal or sagittal view.
Number of CT Slices: If you chose the slice method, count the slices that show the bleed. Score each slice against the biggest one: 1 if it is over 75%, 0.5 if it is 25–75%, and 0 if it is under 25%.
CT Slice Thickness: Type how thick each slice is and pick mm or cm. The tool then shows your calculated C value.
Display volume in: Choose how you want the answer shown: mL, cm³, L, in³, or fl oz.
Press Calculate Volume to see your result, chart, and steps. Press Clear All to start over. If a box is marked "Unknown" or left empty, the tool will show you which field to fix.
What Is an ICH Volume Calculation?
An intracerebral hemorrhage (ICH) is bleeding inside the brain itself. On a CT scan, the blood shows up as a bright spot called a hematoma. Doctors need to know how big that spot is. The size, measured in milliliters (mL), is called the ICH volume. It helps the care team judge how serious the bleed is and what to do next.
The ABC/2 Formula
The ABC/2 method is a fast way to estimate bleed size at the bedside. It treats the hematoma like a simple oval ball.2 You multiply three lengths and divide by two:
- A is the longest line across the bleed, on the CT slice where the bleed looks biggest.1
- B is the longest line that crosses A at a right angle, on that same slice.1
- C is how tall the bleed is from top to bottom (head to foot).1
All three are in centimeters. Because 1 cm³ equals 1 mL, the answer comes out directly in milliliters.
Finding the C Measurement
You can measure C straight from a coronal or sagittal view. Or you can count CT slices. Look at every slice that shows blood and compare it to the biggest slice:
- Count it as 1 if the blood covers more than 75% of the biggest area.
- Count it as 0.5 if it covers about 25% to 75%.
- Count it as 0 if it covers less than 25%.
Add the counts, then multiply by the slice thickness to get C.1
When to Divide by 3 Instead of 2
ABC/2 works best for round or oval bleeds. If the hematoma is lumpy, spread out, or broken into separate parts, ABC/2 can make it look bigger than it really is.7 In those cases, dividing by 3 gives a closer estimate.7
Why the Number Matters
Bleed size is one of the strongest clues about how a patient will do.2 Larger bleeds press harder on brain tissue and raise the risk of swelling and poor outcomes. Volumes above 30 mL are linked to worse results, and volumes above 60 mL are very serious.2 The calculator places your result in the volume groups that study used: less than 30, 30 to 60, and greater than 60 cm³.2 Volume is also part of the ICH Score, a common tool for judging risk.3 Repeating the measurement later can show if the bleed is growing, which often happens in the first few hours.5
Keep in Mind
This is an estimate, not an exact number. It can also differ from a computer measurement of the same scan: in one large study, only about half of ABC/2 readings were within 20% of the computer volume, and the formula tended to overestimate.4 The math also assumes a smooth shape, which real bleeds rarely have. Always read the number next to the scan, the exam, and the whole clinical picture.