A quarter note lasts for beat in common time.

A quarter note lasts for one beat in common time.

A quarter note in common time, also known as 4/4 time, lasts for one beat. In music notation, it is typically represented by a solid notehead with a stem. When counting beats in a measure, each quarter note would receive one count. For example, in a measure of 4/4 time, it would typically be counted as 1, 2, 3, 4, with each count corresponding to a quarter note.