Boxer and politician Manny Pacquiao is expected to donate half of his earnings from Saturday's boxing match with Floyd Mayweather Jr to charity.

Pacquiao, 36, will receive well over US$100 million (S$133 million) in a 60-40 purse split the fighters agreed to beforehand, with revenues believed to have soared past US$400 million.

He lost to 38-year-old Mayweather on points in the greatly hyped up "fight of the century".

Pacquiao's promoter Bob Arum told reporters before the match: "I'm sure half of what Manny earns in this fight is going to go to charity. That is just Manny. We don't like to talk about money too much as more charities line up."

Boxing great Sugar Ray Leonard had earlier warned Pacquiao not to be too generous.

"Pacquiao tries to help everyone, just like me, he goes out of his way to help everyone but you can't help the world," said Leonard.

"Sometimes you have to say 'no'. It was difficult for me to say no at first, I gave away many millions of dollars."

Pacquiao, who is known for his philanthropy, is unlikely to heed his advice.

The Philippine Inquirer called the boxer and two-term congressman the "biggest one-man charity" in the Philippines.