PSA levels are measured in nanograms per millilitre of blood (ng/ml). Whether a PSA level is “normal” depends on the individual and their age. Cancer Research UK uses the following rough guide: 1  3 ng/ml or lower is considered in the normal range for a man under 60 years old. 2  4 ng/ml or lower is normal for a man between 60 to 69 years old. 3  5 ng/ml or lower is normal for a man 70 years old and over.