This question isn't exactly limited to the video game (there's also the Archie Comics books and a TV series), but was there ever a canon answer on how fast Sonic can run? In his Super Sonic or Hyper Sonic states? I suppose one would have to assume he's running on a flat surface.
This wiki answer "How fast does sonic run in full speed" lists Sonic's increased speeds as he evolved through the games and shows.
- Originally he was said to be the speed of sound, at 767+ miles per hour at sea level.
- In Sonic Unleaded the check points would report his speed in excess of 2500 miles an hour.
- The Sonic Adventure DX manual lists him at least as fast as 3840 miles an hour (hypersonic)
- After that he developed light speed attacks and the ability to travel at light speed and to freeze time.
Like most super powered characters, his powers keep expanding to extend the story. Soon he will be able to transcend both time and space.
Officially, and technically, Sonic can run briefly at light speed, with the use of the Light Speed Dash power (which itself requires the Light Speed Shoes).
This screencap is from Sonic Adventure 1.
For purposes of game play, Sonic's movement at this speed is not accurately depicted in the games.
Okay Sonic basically has no limits to his speed but it is recorded his average speed is 767 miles per hour, this means he can break the sound barrier in mere seconds, but it was mentioned sonic can go light speed confirmed by the creator of Sonic, but this drains alot of chaos energy, but Sonic's speed can be affected by some environments like icy areas and muddy areas as well, but he is fast enough to run on water due to his speed and weight, lastly his speed is unknown but it is definetly faster than sound he will increase his speed in future adventures and stories
In Sonic Unleashed Sonic the Hedgehog clocked through the check point of 2887 miles per hour, which means this would be 4646.2 kilometers per hour but Sonic can further increase his speed to 3000 miles per hour with his figure 8 technique and spin dash, this would be approximately be 4828 kilometers per, this incredible speed would equal to 1341 meters per second.
Sonic's speed is unknown but clocked in an average of 765 miles per hour as Sonic goes through more adventures his speed would increase greatly. He has no limits to his speed therefore this can be a possibility or fact, Although with all chaos emeralds to summon the form of Super Sonic, this form is a 1000% power increase so if we calculate his speed: 1000*4828= 4 828 000 kilometers per hour in flight mode it would increase approximately 5 000 000 kilometers per hour and compare to the speed of light (1.07925285*10 to the power of 9) this means Super Sonic can nearly reach the speed of light at full top speed and hyper form is 2000% increase and his most powerful form hyper shadic, 1 trillion% this means its 482800000000000000000000 kilometers per hour/compare to the speed of light 1079252850 kilometers per hour this means HYPER SHADIC is 44 734 417.2 times faster than light.
This proves that Sonic the Hedgehog is THE FASTEST THING IN LIFE!!!!!!
(I can't comment, so I'll edit the answer instead. This guy made a fatal mistake calculating sonics speed. While he was right at first, he didn't factor in the 1000% speed increase from super form correctly. He multiplied his base speed by 1000, when a 1000% increase is only a mere 10 times his original max speed. That means his max speed in super form is actually only 48280 kilometers per hour. Otherwise, it was a passable theory. Thank you for your time.)