Dear sir,
Thank you for your query at DoctorSpring.com
The only way to increase the size of penis without surgery is the use of penile extenders.
However they are very difficult to use and have to be used for fairly long period of time.
And these comes with a lot of complications and risks of injuries. The only natural way is the process of jelqing, which can add another 2-3 cms.
Take care
Sincerely
Rajiv Goel