The estimate is the most complete report ever, reflecting data from 90 national surveys. It shows that 70 million more women and girls are affected by the practice than estimated in 2014.
The report notes that half of those affected by female genital mutilation (FGM) live in Egypt, Ethiopia and Indonesia.
About 44 million of those who have undergone FGM are currently under14 years of age.
"In every case FGM violates the rights of girls and women," said Geeta Rao Gupta, Unicef deputy executive director.
"Determining the magnitude of female genital mutilation is essential to eliminating the practice."
- DPA