PSA Density is a tool to correlate a patient's PSA with his prostate volume. One of the most important parameters that can confound PSA interpretation is prostate volume. A larger prostate results in more cells and a corresponding increase in PSA production. Benign prostatic hypertrophy is therefore a typical non-cancerous condition in which PSA may be elevated.

To eliminate the influence of glandular volume in the "reading" of a PSA value, PSA density was introduced, which corresponds to the proportion of PSA produced by each cubic centimeter of gland. The cut-off value was set at 0.15: higher values lead to an increased risk of prostate cancer.