Piano notes

The notes on a piano form the basis for so-called scientific pitch notation^↗, which is commonly used to identify musical pitches. On a standard 88-key piano keyboard, the notes range from a low of A₀ (at a frequency of 27.5 Hz^↗) on the left to a high of C₈ (at just over 4186 Hz) on the right.

Wikipedia has information about:

Piano key frequencies^↗

The non-numeric part of the notation is the name of a musical note^↗, from A to G, with possible sharps^↗ (♯) and flats^↗ (♭) on most of those notes. The subscripted number in the notation refers to which octave the note is in. Despite the fact that the leftmost key is an A, each octave starts on a C key (C₁ corresponds to the third white key from the left—the second white key from the left is B₀, not B₁).

In each octave, there are 7 white keys corresponding to the notes C, D, E, F, G, A, and B, and 5 black keys corresponding to (depending on the key^↗ one is playing in) C♯ or D♭, D♯ or E♭, F♯ or G♭, G♯ or A♭, and A♯ or B♭. Thus there are a total of 12 keys per octave, each of which differ by what is called a semitone^↗. Each higher octave is pitched at twice the frequency of the previous one—so, for example, the frequency of C₂ (65.4064 Hz) is twice that of C₁ (32.7032 Hz).

The frequencies stated here are for an idealized piano with standard equal temperament^↗ tuning and differ slightly from real-world pianos tuned in that way. See the various Wikipedia articles, especially the one linked to in the box above, for more details about all of this.

References

There are no individual references. All of the information here is based on the various Wikipedia articles linked to above.