Stage 3 – Rapid Growth Stage

Typical Age Range

This stage starts when the adolescent growth spurt begins and ends when the rapid growth period slows down. On average it starts around age 13.5 but can start as early as 10 or as late as 17. It typically lasts about two years.

Characteristics and Changes During Stage 3:


Growth spurt occurs in this stage, growing at a typical rate of about 3 to 8 inches (7 to 20 cm) per year. It is the rising rate of growth that is considered the prime marker for the start of stage 3.


The scrotum takes on a hanging appearance when warm. One testicle, usually the left, will hang lower than the other. Testes are between 1 1/4 to 1 1/2 inches (3.6 to 4.1 cm) measured in length along the long axis or measured in volume they are 6 to 12 ml.

The penis continues to grow, but mostly in length. The glans at the end of the penis darkens in color.


Pubic hair darkens and becomes curly, spreads across the groin, though not real dense. Hair under arms becomes noticeable.


Voice begins to crack as the voice box gets larger.


Ring (areola) darkens around the nipples.

Breasts stand out on about half of all boys as fat accumulates under the nipples. One breast might stand out more than the other.

The arms and legs lengthen, which is what gives the rapid increase in height. A boy in stage 3 looks long-legged compared to an adult’s proportions. He also tends to be thinner during this stage, both because muscles are stretched further and because rapid growth consumes a lot of energy.


Moodiness becomes noticeable as hormones fluctuate wildly.


There is a huge increase in appetite as the body tries to keep up with the energy needs for growth.

Time lapse of each week from age 14 to 16.