What was James Bradley's calculation to calculate the speed of light?
Despite many online sources crediting James Bradley with having calculated the speed of light to a 295.000 km/sec (britannica) or 301.000 km/sec (wikipedia), a small nuance ought to be added. Like Ole Romer before him in 1676, James Bradley calculated the speed of light relative to something else but both never provided a value in Earth-based units.

He wrote,


  This therefore being 20’’,2, AC will be to AB that is the Velocity of Light to the Velocity of the Eye (which in
  this Case may be supposed the same as the Velocity of the Earth's
  annual Motion in its Orbit) as 10210 to One from whence it would follow
  that Light moves or is propagated as far as from the Sun to the Earth
  in 8’ 12’’.
  
  (source)


The calculation to get to the ratio of 10210 is,

size of a radian (206265’’) / angle of aberration (20’’,2)


This ratio also holds for the speed of light to the speed of the earth. Not sure though exactly how britannica and wikipedia arrive at their respective values.