LOS ANGELES (AFP) - Floyd Mayweather, who is fighting twice in the same calendar year for the first time since 2007, weighed in lighter than his Mexican rival Saul Alvarez on Friday.

The boisterous crowd of about 12,000 that squeezed into the MGM arena in Las Vegas cheered loudly when Alvarez tipped the scales right on the catch weight of 152 pounds (68.9kg) one day ahead of their 12-round world championship bout for the super welterweight title held by the Mexican boxer.

The world's highest paid athlete Mayweather, who weighed in at 150.5 pounds, will put his perfect record on the line when he squares off against Alvarez in a showdown between the two undefeated boxers.

The fight with Alvarez is the second in Mayweather's six-bout, 30-month contract with American cable network Showtime that could pay him more than US$200 million (S$254 million).