The length of time it takes to sing the Happy Birthday song is around 21 seconds.
When I counted the time it took to sing Happy Birthday it took me 21 seconds.
It normally takes between 20 to 22 seconds from start to finish to sing happy birthday to someone depending on how long you pause between the lyrics and how long the persons name is.
But for me it takes around 21 seconds to sing the Happy Birthday song completely.
When washing your hands through it's a good idea to sing the Happy Birthday Song when washing your hands because you need to wash your hands for at least 20 seconds to kill the germs and viruses that can be on the hands.