This study aimed to establish a reference range of penile length and circumference of adult males in China, and to compare the penile dimensions of different ethnical backgrounds. To do this, penile length and circumference measurements were obtained from 5196 healthy males attending the Urology Counseling Clinic. The mean value of penile dimensions was a flaccid length of 6.5 ± 0.7 cm, a stretched length of 12.9 ± 1.2 cm and a flaccid circumference of 8.0 ± 0.8 cm. In the subgroup of 311 males, the mean erectile length was 12.9 ± 1.3 cm and the mean erectile circumference was 10.5 ± 0.9 cm, the mean flaccid and erectile glans lengths were 2.7 ± 0.3 and 3.4 ± 0.4 cm, respectively, and the mean flaccid and erectile glans diameters were 2.6 ± 0.2 and 3.4 ± 0.4 cm, respectively. We found that flaccid penile length and circumference varied among different ethnicities. This study established a reference range for penile dimensions, which will help when counseling patients worried about their penile size or seeking penis enlargement surgery. We also found that penile dimensions are different in different ethnicities, but further investigations are needed to validate this.