Between what ages do most girls have their period?

The average age for a girl to have her first period, also known as menarche, is between 12 and 13 years old. However, it is important to note that this can vary widely, with some girls starting as early as 8 years old and others not starting until their late teens. This variation is influenced by a number of factors, including genetics, ethnicity, body fat percentage, and overall health.