Health calculators

ICH Volume Calculator

Updated Sep 23, 2026 By Infinity Calculator
Rate Formulas Medical disclaimer

Hemorrhage Shape

Select "Round / Ellipsoid" for most typical hematomas. Select "Irregular, Separated, or Multinodular" for complex or multicompartmental hemorrhages.

Measurements

Input Unit System
Switching units converts every entered measurement automatically. The calculated volume is always reported in mL (cm³) and can be shown in other volume units in the results panel.
Axial CT slice diagram showing the A and B measurement axes A simplified axial CT slice of the head. The hemorrhage is drawn as a shaded oval. Axis A runs along the longest diameter of the hemorrhage. Axis B runs across the hemorrhage perpendicular to axis A, on the same slice. A B A = longest diameter  ·  B = longest diameter perpendicular to A
Measure A and B on the same CT slice that shows the largest hemorrhage area.
Longest diameter of the hemorrhage on the CT slice with the largest area.
cm
Greatest diameter perpendicular to Length (A), measured on the same CT slice.
cm

Craniocaudal Dimension (C)

Weighted count of the axial slices on which the hemorrhage is visible.
6 slices
Count each slice relative to the one with the largest hemorrhage area: 1.0 if >75%, 0.5 if 25–75%, 0 if <25%.
Scanner-native reconstruction thickness of each axial slice.
Slider range: 0.5 mm – 7.0 mm.
Calculated C: 3.0 cm (30.0 mm)
ICH Volume Result
24.00 mL
≡ 24.00 mL (cm³) · 1.46 in³ · 0.0240 L
Calculated using ABC/2 (Round / Ellipsoid)
(5.00 cm × 3.20 cm × 3.00 cm) ÷ 2 = 24.00 mL
Estimated range
19.20 – 28.80 mL
Range reflects typical inter-observer measurement variability (±20%). This is an estimate, not a precise interval.
Volume classification
Volume Classification: Moderate
Moderate hematoma volume band: 10 – 30 mL.
Volume on Clinical Reference Scale
Reference bands: Small < 10 mL  ·  Moderate 10–30 mL  ·  Large 31–60 mL  ·  Critical > 60 mL
Step-by-Step Solution
Structured Findings Text

        

          
          
        

      

    


  




        


                
        
        
        
        
        
        

                    

            

                
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. 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. You enter three things:



    
  
  • A is the longest width of the bleed on the CT slice where it looks biggest
    • 
  
  • B is the widest part that crosses A at a right angle, on that same slice
    • 
  
  • 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.



The result shows the volume in mL (cm³), an estimated range for measurement error, and a simple size band: small, moderate, large, or critical. 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 size class, 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. 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.
    • 
  
  • B is the longest line that crosses A at a right angle, on that same slice.
    • 
  
  • C is how tall the bleed is from top to bottom (head to foot).
    • 



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.



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. In those cases, dividing by 3 gives a closer estimate.



Why the Number Matters


Bleed size is one of the strongest clues about how a patient will do. 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. Volume is also part of the ICH Score, a common tool for judging risk. Repeating the measurement later can show if the bleed is growing, which often happens in the first few hours.



Keep in Mind


This is an estimate, not an exact number. Two people measuring the same scan can get answers that differ by about 20%. 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.
            

        
                    

            

                
Formulas used

                                    

                                                ICH volume (ABC/2 or ABC/3)
                        
V = \frac{A \times B \times C}{d}, \quad d = 2 \text{ (ellipsoid)},\; 3 \text{ (irregular)}

                    

                                    

                                                Craniocaudal dimension C from CT slices
                        
C_{\text{cm}} = \frac{N_{\text{slices}} \times T_{\text{mm}}}{10}

                    

                                    

                                                Length unit conversion (mm to cm)
                        
L_{\text{cm}} = \frac{L_{\text{mm}}}{10}

                    

                                    

                                                Estimated volume range (\pm 20\% inter-observer variability)
                        
V_{\text{low}} = 0.80 \times V, \qquad V_{\text{high}} = 1.20 \times V

                    

                                    

                                                Volume unit conversion from mL
                        
V_{\text{unit}} = \frac{V_{\text{mL}}}{f}, \quad f_{\text{mL}}=1,\; f_{\text{cm}^3}=1,\; f_{\text{L}}=1000,\; f_{\text{in}^3}=16.387064,\; f_{\text{fl oz}}=29.5735295625

                    

                                    

                                                Volume classification bands
                        
\text{Class}(V) = \begin{cases} \text{Small} & V < 10\ \text{mL} \\ \text{Moderate} & 10 \le V \le 30\ \text{mL} \\ \text{Large} & 30 < V \le 60\ \text{mL} \\ \text{Critical} & V > 60\ \text{mL} \end{cases}

                    

                            

        
                    

            

                
Frequently asked questions

                

                                            

                            
What ICH volume is considered dangerous?

                            
Bigger bleeds are more dangerous. A rough guide:
  • Under 10 mL – small, often better outcomes
  • 10–30 mL – moderate
  • 31–60 mL – large, higher risk
  • Over 60 mL – critical
In a well-known study, patients with a bleed over 60 mL plus a low level of consciousness (GCS 8 or less) had about a 91% death rate at 30 days. Patients under 30 mL with a better GCS had about 19%.

                        

                                            

                            
Why is ABC/2 divided by 2?

                            
It comes from the volume of an oval ball (ellipsoid). That formula is 4/3 × π × the three radii. Since each radius is half of A, B, or C, the math becomes A × B × C × 0.52. That is almost exactly the same as dividing by 2. So ABC/2 is a shortcut you can do in your head at the bedside.

                        

                                            

                            
How is ICH volume used in the ICH Score?

                            
The ICH Score adds up points to predict 30-day death risk. Volume is one of five parts:
  • ICH volume 30 mL or more = 1 point (under 30 mL = 0)
  • GCS 3–4 = 2 points, GCS 5–12 = 1 point
  • Blood in the ventricles = 1 point
  • Bleed below the tentorium = 1 point
  • Age 80 or older = 1 point
Higher total scores mean higher risk.

                        

                                            

                            
What counts as hematoma expansion on a repeat CT?

                            
Expansion is usually defined as the bleed growing by more than 33% of its first volume, or by more than 6 mL. To check, measure the volume the same way on both scans. Growth most often happens in the first few hours after symptoms start.

                        

                                            

                            
How fast does a brain bleed grow?

                            
Growth is fastest early. About one in three bleeds get bigger within the first 3 hours after symptoms begin. Growth after 24 hours is uncommon. This is why a repeat CT is often done within 6 to 24 hours.

                        

                                            

                            
At what volume is surgery considered for a brain bleed?

                            
There is no single cutoff. General patterns:
  • Cerebellar bleeds bigger than 3 cm across (roughly 15 mL or more) often need surgery, especially with brainstem pressure or hydrocephalus.
  • Lobar bleeds near the surface around 20–30 mL may be considered if the patient is getting worse.
  • Deep bleeds in the basal ganglia or thalamus usually do not benefit from open surgery.
The decision also depends on age, GCS, and how fast the patient is changing.

                        

                                            

                            
Does ABC/2 work for subdural or epidural hematomas?

                            
Not well for subdural bleeds. Those are crescent shaped and wrap around the brain, so ABC/2 tends to overestimate them. Some centers use ABC/3 or modified formulas instead. Epidural bleeds are more lens shaped, so ABC/2 does better, but it is still an estimate.

                        

                                            

                            
How do you measure blood in the ventricles (IVH)?

                            
Measure it separately from the brain bleed. ABC/2 is a poor fit for blood inside the ventricles because the ventricles have a branching shape, not an oval one. Most teams grade IVH with a scale like the Graeb or modified Graeb score instead of a volume number.

                        

                                            

                            
Is 1 cc the same as 1 mL when measuring a brain bleed?

                            
Yes. One cubic centimeter (cc or cm³) equals exactly one milliliter (mL). Radiology reports use both words for the same thing, so a 25 cc bleed and a 25 mL bleed are identical.

                        

                                            

                            
What CT slice thickness is used to measure ICH volume?

                            
Standard head CT scans usually use 5 mm slices through the brain. Thinner slices, like 1.25 mm or 2.5 mm, give a more exact height measurement but take more counting. Always use the real reconstruction thickness of the images you are looking at, not the scanner setting.

                        

                                            

                            
Is ICH volume more important than midline shift?

                            
They tell you different things. Volume tells you how much blood is there. Midline shift tells you how much the brain is being pushed. A large bleed often causes shift, but swelling and location matter too. A small bleed in the brainstem can be deadly with no shift at all. Doctors look at both.

                        

                                    

            

        
        
                    

            

                

                    
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