(Copied directly from my pastebin)
Let's put into perspective how overpowering goku really is, using only the DBZ canon.
Before you read any further, please note that I am using Power levels as my basis. The powerlevels I use are found here: (dragonball.wikia.com/wiki/List_of_power_levels). All power levels that I take are from the Official Daizenshuu. They represent the Maximum strength output for that character. All Powerlevels were discontinued after the frieza saga, and therefore any power level afterwards is mere speculation. I will be skewing goku here so that he is weaker than he would be, so that I can remain in line with the DBZ canon
Vegeta, during the saiyan saga has a Power level (PL) of 18,000. With it, his galick gun would've blown up earth, had goku not stopped him (http://www.youtube.com/watch?v=RiCrprzMqME).
When he first turns super saiyan, goku has a PL of 150,000,000. Assuming that all vegeta could've destroyed is the one planet, goku's power would allow him to destroy a being with power equal to 8,333.34 planets. Without progressing goku's power level any further, since there are no canon official power levels after that, we'll simply use that value and apply transformations.
SSJ1 = 150,000,000
SSJ2(SSJ1x2) = 300,000,000
SSJ3(SSJ2x4) = 1,200,000,000
((SSJ4 is uncanon, and will not be used.))
As a ssj3 without progressing goku's base power any further since the frieza saga, goku can destroy the equivilant of 66,666.67 planets
Along with this,vegeta took goku's 32,000 PL Kaio-Kenx4 kamehameha + his own 18,000 PL Galick Gun. That totals to a PL of 50,000, giving the combined beams the power to destroy 2.78 planets. From this, one can infer that saiyans can withstand an attack of equal or lesser planet-busting capability of 2.78x your own. Meaning SSJ3 goku without progression can tank an attack that can destroy 185,333.34 planets.
Goku, in dragonball runs the 100m in 8s (http://www.youtube.com/watch?v=RqFHPNSPL8U). That yeilds him a speed of 12.5 m/s. Meaning that 1PL = 1.25 m/s (for saiyans). Goku as an SSj3 would have a speed of 1,500,000,000 m/s. 5 times the speed of light (299,792,458). Applying relativity, Goku in SSJ3 would be traveling at 298,970,962. That's more than 99.7% of the speed of light (Thanks to Sunny Sanity from gaiaonline!)
Also in dragonball, a young kid goku (PL 10) is shown picking up a car and throwing it(http://www.youtube.com/watch?v=dJMEmEuEKW0). The car seemed similar to the Mini Cooper S Countryman ALL4 (http://mt.kargo.com/entry/view/id/6255/pn/all/p/0/?KSID=bjprizxtkkz). The Cooper weighs 1.6275 tons or 3255lbs. This gives saiyans 325.5lbs/1PL of RAW lift strength, as goku was unable to utilize Ki energy at this point in the series. SSJ3 Goku without progression has a Raw lift strength of 390,600,000,000lbs, or 195,300,000 tons.
Utilizing Ki would augment goku's already immense natural physical attributes.
And to top it all off, all of these values are horrendously lower than the power level post-battle of the gods because no official values for power levels were posted for goku after the frieza saga.
However, we can manually calculate goku's PL to get closer to what it may actually be.
(Quoted from Laurcus on comicvine, edited out parts referring to SSJ4 as it is irrelevant: http://www.comicvine.com/goku/4005-19765/forums/what-is-ssj4-gokus-power-level-in-gt-740635/)
"SS1 Goku during the Frieza saga was 150 million. When Vegeta left the Hyperbolic Time Chamber Goku stated that he would have had to have gotten 3 times stronger to even stand a chance against Semi-Perfect Cell. It's generally accepted that Goku and Vegeta were about equal pre HTC. So assuming Goku did NOT get stronger from his fight with Frieza and 4 more years of training, that puts SS1 Vegeta at 450 million. Later, when Goku leaves the time chamber, he powers up for Korin. His level of power greatly alarms Vegeta and Trunks, this indicates Goku is now greater than or equal to Vegeta. Goku then reveals to Korin that he only used about half of his power. That puts FPSS Cell saga Goku at 900 mil. Same song and dance for Gohan. Through the course of the story it's revealed he is equal to Goku. Then Gohan goes SS2, which is twice as strong as SS1 according to the Super Exciting Guide. That puts SS2 Gohan at at least 1.8 billion.
Then you get into the Buu saga. SS3 is another x4 on top of SS2, so assuming Goku didn't get any stronger in his 7 years of training, that puts him at 7.2 billion...Supreme Kai states in episode 219 that he is 1000 times stronger than Frieza. As you already pointed out, Frieza = 120 million, times 1000 and you have 120 billion. In Kibito's Daizenshuu entry, it says that Kibito could fight evenly with base form Gohan. Now, if you recall, Supreme Kai was repeatedly outmatched by the Saiyans even in base form. He was scared that even working together, they would not be able to beat Pui Pui, yet Vegeta does so easily, a feat that does not impress Goku or Gohan. It's safe to say that Gohan, (and by proxy Kibito) has a power level much higher than 120 billion at that point, in base form. For the sake of being as conservative as possible though, I'll assume Kibito has a power level of exactly 120 billion.
In the Super Exciting Guide, on page 63, it states that fusion via the earrings is in fact multiplication of power levels. That means Kibito Kai has a power level of at least 14.4 sextillion. Kibito Kai, by his own statements, as well as the statements of Old Kai, Goku and Vegeta, was so weak he would have just been in the way if he tried to fight Buu. Even when Vegeta was trying to fight Kid Buu in base form, Old Kai still warned Kibito Kai that he's too weak to help. From this we can conclude that base form Goku and Vegeta > 14.4 sextillion. Why is there such a giant gap in their power between the fight with Kid Buu and the start of the Buu saga? *shrugs* I don't know. The only thing I can think of is zenkai boosts. That, or Gohan was much much weaker than Goku and Vegeta...And as I've demonstrated, that's lowballing at every point possible, and completely ignoring Goku's 15 years of training after the fight with Kid Buu."
Meaning that by the end of the buu saga, goku's PL is 14.4 sextillion in base.
Pre-BoG Goku base
Destructive Force: 800,000,000,000,000,000 Planets
Durability: 2,224,000,000,000,000,000 Planets
Speed: 18,000,000,000,000,000,000,000 m/s (60,206,515,975,956.22 x Light)
Raw Lift: 2,343,600,000,000,000,000,000 tons
Goku can also use kaio-ken to multiply his already immense power level. He's been shown going up to kaio-ken x 20, so that's the max i'd reference. SSJ3 pre-god goku using kaio-ken x 20 allows him to destroy 1,333,333.4 planets, tank 3,706,666.9 planets, move at 30,000,000,000 m/s (80x the speed of light). His lift strength is 3,906,000,000 tons. His PL is 24,000,000,000.
Vegito is the potora fusion of goku & vegeta, and as stated above, would have goku & vegeta's power levels multiplied together. Meaning that Vegito had a PL of around 207,360,000,000,000,000,000,000,768,400,016,360,888,208,504, or 2.0736e+44 in BASE. Vegito as a Super Saiyan would be 10,368,000,000,000,000,000,000,368,720,352,568,464,216,720,200 or 1.0368e+46.
(Using http://www.easysurf.cc/scintd.htm to display values out of scientific notation)
Now to further goku's power. Please keep note that these values will still be lower than they should be, but will get you closer to what it might be at the end of BoG.
Bills is stated to be the strongest character in the history of DBZ. That means he trumps vegito. SSJ1 Goku after attaining super saiyan god is shown to be on par with bills. Bills must be stronger than Vegito, but there is no value to give him. He may be 1.1x stronger or 100x stronger. I don't know. But what I do know is that...
SSJ1 goku post BoG = Bills > SSJ3 Goku Pre-BoG
SSJ1 = 10,368,000,000,000,000,000,000,368,720,352,568,464,216,720,200 (1.0368e+46)
SSJ2(SSJ1x2) = 20,736,000,000,000,000,000,000,736,440,704,136,928,432,440,400 (2.0736e+46)
SSJ3(SSJ2x4) = 82,944,000,000,000,000,000,000,944,760,816,544,712,728,760,600 (8.2944e+46)
With these values...
Destructive Power: 4,607,999,999,999,999,488,712,088,728,448,976,984,864,888 Planets
Durability: 12,810,240,000,000,002,048,152,560,088,416,368,320,448,224 Planets
Speed: 103,680,000,000,000,000,000,000,384,200,008,680,944,104,752,496 m/sec (346,789,532,021,507,840,472,584,848,560,232,928,288 xSpeed of Light)
Raw Lift: 13,499,136,000,000,002,048,152,056,752,928,128,272,528,424,048 Tons
PL: 1,658,880,000,000,000,000,000,000,144,200,128,880,104,664,032,936 (1.65888e+48)
Destructive Power: 91,260,000,000,000,000,000,968,440,024,576,296,560,096,200 Planets
Durability: 256,204,800,000,000,000,000,000,056,304,376,128,440,552,480 Planets
Speed: 2,073,600,000,000,000,256,144,456,888,320,904,920,696,400,384,176 m/sec (6,935,790,640,430,156,776,296,048,792,824,128,128,848 xSpeed of Light)
Raw Lift: 269,982,719,999,999,936,464,136,608,336,656,480,088,744,688,976 Tons
His destructive force alone is enough to destroy the Universe 92,160,000,000,000,000,000 times over, and survive the explosion. (http://scienceblogs.com/startswithabang/2013/01/05/how-many-planets-are-in-the-universe/ calcs the number of planets in our universe at about 1,000,000,000,000,000,000,000,000.)