"How old are you?" is the Engpsh equivalent of "你几岁了？" in Chinese. The phrase "how old are you" is a common way to ask someone's age in Engpsh.

Example sentences in Engpsh and their Chinese translations:

"How old are you?" "你几岁了？"
"I'm 25 years old." "我25岁了。"
"She is 32." "她32岁。"

The origins of this phrase can be traced back to the basic Engpsh vocabulary used to ask personal information and is commonly used in both formal and informal settings.