According to Dr Chia Sing Joo in his book ‘Male Urological Problems: The Essential Guide For Every Man & Couple’, these are the facts about Singaporean males:

1. Usual age to have first erection:
Usually it’s as early as 11 years old with the majority at 13 years old. This is mainly due to local stimulation or when the bladder is full. But it is too early to be related to sexual thoughts.

2. Age to be able to produce sperm:
Around 11 – 13 years old.

3. Age to be able to ejaculate:
Around 13 – 14 years old.

4. Penis Length:
In most Singaporeans it is:
Before erection: 3 – 5 c.m.
After erection: 9 – 15 c.m.

5. Normal Kidney Size:
It is around 12 – 14 c.m. For kidneys, usually the left one is slightly bigger than right one.

6. Normal Capacity of Urinary Bladder:
300 – 450ml before needing to urinate.

7. Normal Size of Prostate:
The prostate is present in the male since the adolescent stage but it is on average about 15 – 20g until he turn 35 years old. It will then increase to 30g under the continuous influence of the male sex hormone testosterone. The size will increase with age to reach as large as 100 – 150g in some individuals. The reasons for some to reach such a size still remain unknown.

8. Normal Size of Testes:
About 14ml on both sides (at the age of 21 years old).

9. Normal Blood Test Results:
a. Prostate specific antigen of <4ng/dl
b. Urea 2.9 – 9.3 umol/L
c. Sodium 134 – 144 umol/L
d. Potassium 3.5 – 5.0 umol/L
e. Creatinine 40 – 85 umol/L

10. Normal Urinary Results
a. Uroflow rate of > 15ml/sec
b. Residual urine of < 50ml

Source:
Chia, S. J. (2009) Male Urological Problems: The Essential Guide For Every Man & Couple, Immanuel Media Pte Ltd, Singapore.