One way to name a black key is to use a sharp symbol (#)…

Sharp means the very next note up (to the right).

For example: F# is a black key, the very next note up from F…

And here are all the black keys named using sharps…

By the way, a sharp does not have to be a black key. Two white keys can also be named using a sharp. Notice that B#, the very next note up from B, is a white key and E#, the very next note up from E, is also a white key…

Putting it all together, here are all seven possible sharps…

learn more… Names of the Piano Keys: Flats