Ok i made calculations
I took the average male
and Then used the average proportion of his stature
which is 8 feet
or 243 Centimeters
then we turn that into a percentage
and we get that 10% of his lenght consists of his dick
Im gonna go with an estimate of his dick being 26 CM
I have made calculation and the average penis is 12 cm
so if we double this amount we reach that 26 CM
To calculate the dick weight of Thanos we grab the average weight of a normal Human Dick this would be aproximately 0.737088 KG
Then we Divide this to the weight of an average human is 80.7 KG or 178 Pounds
This mean that the percentage of an average human dick is 0.9% of their weight
If we apply the same concept for Thanos and say his dick is 0.9 percent of his body weight it would weigh aproximately 4 kg.
(If someone figures out how much percentage of his body is Muscles I can recalculate this and maybe make a graph depends on if im feeling it)