It is reported separately from the total PSA. The % free PSA is calculated as the free PSA divided by the total PSA times 100. (Free/Total x 100) A %free PSA of more than 25% means that there is about an 8% chance that a biopsy would show prostate cancer; whereas, a %free PSA of less than 10% would mean there is nearly a 60% chance that a biopsy would show cancer. Also, lower percentages of free PSA are also more likely to be associated with more aggressive forms of prostate cancer.