"I'm so, so happy with this," Mills told reporters following the closed hearing.
The court also ruled that the couple's 4-year-old daughter Beatrice should receive a "periodical payments order" of $70,000 per annum. On top of that, McCartney will pay for the child's nanny and school fees.
"I'm so glad it's over," Mills said at her impromptu news conference.
"It was an incredible result in the end to secure mine and my daughter's future and that of all the charities that I obviously plan on helping and making a difference with -- because you know it has been my life for 20 years," she said.
McCartney left the court without making any statement. While pleased with the financial settlement, Mills intends to appeal to prevent publication of the details of the settlement for the couple's daughter.
McCartney, 65, and Mills, 40, went to court last month to decide on Mills' share of his fortune, which had been estimated at as much as $1.6 billion.
Judge Hugh Bennett, however, found that the total value of all of McCartney's assets, including his business assets, was about $800 million.
Mills said the settlement vindicated her decision to fire her lawyers. The legal fees, she said, instead "could easily go to charity."
"Obviously the court do not want a litigant in person to do well, it's against everything that they ever wish, so when they write the judgment up they're never going to make it look in favor," she said.
"But all of you that have researched know that it was always going to be a figure between 20 and 30 million (pounds), Paul was offering a lot less than that, which you'll see in the judgment, and very much last minute to put me and Beatrice sadly through this ... incredibly sad."
Mills had sought almost $250 million, while McCartney had said she should receive $31.6 million, including her own assets, which the court assessed at $15.6 million.
She had harsh words for McCartney's lawyer, Fiona Shackleton, who was well known for representing Prince Charles in his divorce from Princess Diana.
"She has called me many, many names before even meeting me when I was in a wheelchair," said Mills.
The settlement has been a long time coming for the couple, who separated two years ago, after four years of marriage. At the time they said the parting was "amicable" and insisted "both of us still care about each other very much."
But the split has grown fractious since McCartney filed for divorce alleging his wife's "unreasonable behavior."
Mills -- a former model whose left leg was amputated below the knee after a motorcycle accident in 1993 -- claimed McCartney had failed to protect her and their daughter from slander, death threats and other abuse, and accused the media of persecuting her. In November, Mills said she had been "treated worse than a murderer or a pedophile," despite years of work for land mine victims and animal welfare charities.
McCartney met Mills in 1999, the year after the death from breast cancer of his first wife, Linda. That marriage was one of rock's most enduring unions, and produced three children, including fashion designer Stella McCartney.
Mills and McCartney married at an Irish castle in June 2002, amid rumors the former Beatle's children disapproved of their new stepmother. The couple's daughter was born the following year...