Stone, 28, opened up about the issue in a new interview with Out Magazine, explaining that the Hollywood “quote” system is in part to blame.
“At our best right now we’re making 80 cents to the dollar,” Stone said.
The Oscar-winning actress said actors are often paid based on how much they made in a previous production.
“It’s a difficult system because it depends on the kinds of films you’re a part of, the size of your role, how much the movies make at the box office,” she said. “And so much of that changes your pay throughout your career, so I go more to the blanket issue that women, in general, are making four fifths at best.”
For the interview, Stone was joined by her Battle of the Sexes costar Andrea Riseborough and retired tennis pro Billie Jean King — whom Stone will portray in the upcoming film.
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Riseborough, who portrays King’s then-secret lover Marilyn Barnett in the film, added that very few women have “quotes” as high those of men because “most films are about white males.”
Stone revealed that some of her male costars have willingly helped bridge the gap.
“In my career so far, I’ve needed my male costars to take a pay cut so that I may have parity with them,” she said. “And that’s something they do for me because they feel it’s what’s right and fair.”
She continued: “If my male co-star, who has a higher quote than me but believes we are equal, takes a pay cut so that I can match him, that changes my quote in the future and changes my life.”
For Stone, the issue is about having equal respect for both men and women. “It’s not about, ‘Women are this and men are that.’ It is, ‘We are all the same, we are all equal, we all deserve the same respect and the same rights.’ “
Battle of the Sexes arrives in theaters on Sept. 22.