Hi. The sizes of testicles can vary but not so much as you have mentioned. How is that you have noticed this much big swelling (5/6 times) suddenly at at given time, I mean this should have been noticed a long ago. There is no pain - Indicates me to think of a few things. 1. hydrocele- collection of water in the scrotal sac , which is always painless. and 2. inguinal hernia descending to the scrotal sac, again painless but increases and reduces in size and you can get impulse on coughing or straining; no pain unless there is an obstruction. 3 a remote possibility of a malignancy again painless. The best way to diagnose is a clinical examination by a Surgeon and a good ultrasonography. IF this is hernia, you can not really wait much and needs a surgery to correct. If this is a tumor needs all the great evaluations by an Urologist. IF hydrocele- surgery is a good option and not an urgent thing; can be planned. I hope this clears your query well. Would like to know the follow-up.