Base on the "low feat" of Goku pushing a boulder of that size before his training with Roshi and the other "low feat" of Goku lifting the Giant Piccolo, I Believe Goku is a +100 tons strenght in his normal form, base in the training with King kai and the 2 tons each limb, make me reduce the base form strength to 50 tons, but because Goku post Buu Saga train 10 years waiting for Buu, my estimations of Goku at the end of the manga (Goku going to train with Ubb) is:
....................minimum - Maximum
Normal form: 80 - 150 tons
SSJ1 x 50: 4000 - 7500 tons
SSJ2: 200,000 - 375,000 tons
SSJ 3 x10: 2 000,000 - 3 375 000 tons (Alive, Buu Saga)
SSJ 3 x 50: 10 000 000 - 18 750 000 tons (End of the Manga)
I considere Goku could not go to his maximum power when he fought the Kid Buu, so his body could not stand alive the same when he was dead, so that is why i give him the X10.
I also considere that 10 years of training without stop will allow Goku to control without any problem SJJ 3 and that is why i give his the X 50 as like in the Freeza Saga.
I also considere that the power ups are higher in the Cell Saga when Goku perfected the SSJ 1 level, but i just use the X 50 that Toriyama and the Daisenzhuu stated, so I believe that the strenght is higher, but i have no prove because Goku dont have feats of strenght since his 100 G training, he just fight.