Background and Purpose— A simple estimation method of intracerebral hematoma volume known as XYZ/2 method has been described previously. This method has also been shown to be valid for the estimation of acute subdural hematoma volume. However, chronic subdural hematomas differ in shape and extension from acute subdural hematomas, which makes the validity of the same method in the estimation of hematoma volume questionable. We aimed to determine the value of XYZ/2 method to estimate the volume of chronic subdural hematoma when compared with computer-assisted volumetric analysis. Methods— Computed tomography scans of 28 patients with unilateral hemispheric chronic subdural hematoma were reviewed. Hematoma volumes were measured using 5 different XYZ/2 formulas and compared with volumes measured by computer-assisted analysis. Nonparametric correlation coefficient (Spearman’s ρ) was used in statistical comparison. Results— All 5 formulas showed excellent correlation with the gold standard, proving the validity of XYZ/2 method in the estimation of chronic subdural hematoma volume (level of significance <0.001). Our results suggest that maximum hematoma length and width, which are not necessarily on the same slice, should be used rather than length and width of hematoma on the central slice when using XYZ/2 method in patients with chronic subdural hematoma. Conclusion— This study proves the validity of XYZ/2 technique for the estimation of chronic subdural hematoma volume as well.