Testicular Volume correlated with Tanner score ¹
(based on external physical measurement of length and width)

Tanner Score	Left		Right
	cm3	std deviation	cm3	std deviation
1	4.76	2.76	5.2	3.86
2	6.4	3.16	7.08	3.89
3	14.58	6.54	14.77	6.1
4	19.8	6.17	20.45	6.79
5	28.31	8.52	30.25	9.64

References:
 

1.  Daniel WA, Feinstein RA, Howard-Peebles P, Baxley WD.  Clinical and laboratory observations.  Testicular volumes of adolescents.  J Peds Dec 1982:1010-1012  (Modified:  Permission requested from publisher)