assessing testicular enlargement at puberty

normally the earliest indicator of sexual maturation in boys

See discussion of the newest devices for pubic hair removal at home.

In the healthy child, testicle size increases about a year before pubic hair or any other signs of puberty. Using ordinary calipers, one can easily monitor pubertal status. (In the absence of testicular enlargement, early pubic hair is caused by abnormally high androgen levels. See premature or exaggerated adrenarche.)

But according to Kaplan1, boys’ pubertal status can be accurately determined by testicular volume at a much earlier stage. Early assessment may be particularly important in a situation where “normal” pubertal staging may be changing due to environmental or other unknown factors.

Normal Volume of the Testicle as a Function of Age
(note that testicle size is smaller in boys than in infants)

Age	Width(cm)	Length(cm)	Volume ± SE(cm3)
Birth	  1.0		1.5		1.1 ± 0.14
1-3 mo	  1.2		2.0		1.9 ± 0.11
4-6 mo	  1.0				1.7 ± 0.11
1-10yr	  < 1.0		1.6		0.7 - 0.9
11-12yr	  1.0		1.7 increasing	1.5 increasing
			 to 1.9		 to 2.0
13-16yr			2.3 increasing	5.0 increasing
			 to 3.5		 to 13.0
Adult	  2 - 3		3 - 5		15-20

http://www.ohsu.edu/radiology/teach/kojima/testicle.htm

Formula for calculating the volume of a sphere:
volume = 0.71 * (length in cm) * (width in cm) * (depth in cm)
Testicle depth is normally equivalent to the width.
One cubic cm in volume is also called 1 ml or 1 cm3 or 1 cc

Example:
Using the calipers, you measure a testicle length of 1.7cm and a width of .8cm.
Multiply 1.7 times .8 = 1.36 times .8 (again) = 1.088 times .71 = .77248
So the volume of this testicle is about .77 cubic centimeters, and is within the normal range for a boy under 10 years old.

In healthy males, the left and right testicles may vary slightly in volume, and one may hang lower than the other.

It takes experience to make such measurements accurately, so use these results as only a rough guide. To verify your conclusion, always consult your doctor.

References:
1. Kaplan SA. Clinical pediatric & adolescent endocrinology. W.B. Saunders. Philadelphia, 1982. p. 307-308