Pound-for-pound king Floyd Mayweather weighed in half a pound less than World Boxing Association champion Marcos Maidana on Friday on the eve of their welterweight world title unification fight.
Mayweather, 45-0 with 26 knockouts, stepped on the scales weighing one pound under the 147-pound limit in front of a packed house of about 9,500 at the Grand Garden Arena.
Argentina's Maidana, 35-3 with 31 knockouts, weighed in at 146.5 pounds for Saturday's 12-round bout.
Mayweather is six pounds lighter than in his last fight against Mexico's Canelo Alvarez.
But he looked fit and trim as he stripped off his red and white track suit and stepped onto the scales wearing bright red socks and pink boxer shorts to a loud applause.
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Not many Vegas punters are giving Maidana a chance to upset Mayweather, who is a heavy favourite to retain his WBC welterweight crown and also claim Maidana's WBA belt.
The two boxers engaged in a brief staredown then quietly went their separate ways, with Mayweather telling US pay-per-view telecaster Showtime that nothing is going to get in his way on Saturday night.
Mayweather is also facing some personal issues involving his love life ahead of Saturday's fight.
He was asked if those issues were a distraction for the fight.
"I perform better under pressure," Mayweather said. "Pressure is normal. I love it. I love it. I am ready to fight."
Mayweather announced last month that he and his ex-fiancee, Shantel Jackson, had broken up.
Showtime revealed the breakup happened after Jackson, who had been pregnant with twins, was no longer pregnant.
Mayweather told Atlanta radio station V-103 on Thursday that he initially thought Jackson had a miscarriage then said he found out from Showtime that she terminated the pregnancy without his knowledge.
"They (Showtime) said 'Floyd this was not a miscarriage, this was an abortion.' So I never knew that," Mayweather said.
"I received some information that was false. I was in love with somebody I didn't know."
Boxing fans began lining up outside the arena doors at 6 in the morning, about eight hours before the scheduled weigh-in start. Dozens who tried to get in after seats were filled were turned away.
The fight is the third of the 30-month, six-fight deal worth $US200 million ($A216.39 million)-plus that Mayweather signed with Showtime.
The undercard features British superstar Amir Khan, who will square off against American Luis Collazo in a 12-round fight.
Khan, who hopes a win Saturday will put him in position to fight Mayweather in the fall, weighed in on the 147-pound limit, as did Collazo.
Khan is fighting for the first time in 12 months. He doesn't expect to be rusty after the longest break of his boxing career.
"I had a nice break," Khan said on Friday. "I needed it. My first fight at 147 pounds and I can't wait to put on a great performance."
