The workplace is not designed for families, and that needs to change, philanthropist Melinda Gates told CNBC on Tuesday.

"We need to have a good, paid family medical leave policy," said the co-chair of the Bill & Melinda Gates Foundation. "We're one of only eight countries in the world — in the world — that doesn't have a paid family leave policy. That's crazy."

The Gates Foundation talks-the-talk and walks-the-walk, changing in 2015 its parental leave program for men and women from 12 weeks to 52 weeks.

"We can't accept that less than 14 percent of women have paid family medical leave," Melinda Gates said in a "Squawk Box" interview in New York, where world leaders have gathered for the United Nations General Assembly's annual meeting.

"We have to redistribute the workload at home, and paid family medical leave for men and women helps with that," she said. "In the United States, women do five years of unpaid labor their husbands don't do. We do 90 minutes more a day: make the school lunch, help with the homework, fix the breakfast, drive them to school."

Technology companies have generally been more generous of late with leave for new moms and dads than the rest of Corporate America.

According to career site GlassDoor, Microsoft, which was co-founded by Bill Gates, gives birth mothers 20 weeks of paid leave, while other parents get 12 weeks. Spotify and Etsy offer six months. GlassDoor also highlighted Johnson & Johnson and TD Bank for standout parental leave policies.

"We need to say to men, 'It's OK to go out and to take leave.' Because one of the things when men take leave, they're more involved in raising the children. It's better for him and it's better for the kids," said Melinda Gates, who has two daughters and a son with husband Bill Gates.

On New Year's Day 1994, Bill and Melinda were married after an office romance at Microsoft where Melinda worked from 1987 to 1996. Twenty-four years later, the couple is worth $98 billion and rank No. 2 on the Forbes' list of the world's most wealthy people.