it be the biggest size of LED you can find -lrb- 2.5 '' -rrb- . it be also very bright that you can read it well even with bright sun in the room . my only complain be there be a poor contact between the clock and the base that house the battery compartment . the clock go blank after I fold it down and reopen it again . I have to slap it to get the LED 's to light up again .