The 40-year-old on Friday tipped the scales at 149.5lbs, three and a half lighter than his Irish opponent and four and a half below the light-middleweight limit.
That he weighed in closer to the welterweight limit at which he has so consistently excelled suggests he has chosen to focus on speed, and that would be logical against the bigger McGregor, as he will avoid an excessively-physical fight.
Mayweather has repeatedly insisted Saturday's fight will be the last of his decorated career, and despite the likelihood his ability will make their match-up highly non-competitive, his impressive shape suggests he has thoroughly prepared.
McGregor is adamant the American is in "the worst shape I've ever seen", but Mayweather, who was also loudly booed by the Irishman's fans in his home city as they weighed in, said: "Weight doesn't win fights, fighting wins fights. This won't go the distance: mark my words.”
But what is the tale of the tape as the two men prepare for the biggest fight in the history of combat sports?
Tale of the tape
40 Age 29
49 Fights 0
49 Wins 0
26 KOs 0
0 Draws 0
0 Losses 0
387 Rounds boxed 0
5ft 8in Height 5ft 9in
149.5lbs Weight 153lbs
Orthodox Stance Southpaw
72in / 183cm Reach 74in / 188cm
89 Number of swear words used on press tour 84
7.4m Twitter followers 5.5m
5.5m Twitter mentions since June 14 8m
99,000 Most retweeted tweet since June 14 253,000
£265m Reported estimated wealth £26.5m
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