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Key

C♯ major

The major key on the tonic C♯. It has seven sharps, every note of the scale is raised. On the piano it sounds exactly like D♭ major with five flats, and because that is easier to read, D♭ major is almost always preferred.

Tonic
C♯
Key signature
7 ♯ (F♯, C♯, G♯, D♯, A♯, E♯, B♯)
Tonic chord
C♯–E♯–G♯
Relative key
A♯ minor
Enharmonically the same
D♭ major
Neighbour on the circle of fifths
F♯ major

All seven sharps

The page Key Signatures names the sharps in their fixed series: F♯, C♯, G♯, D♯, A♯, E♯, B♯. C♯ major is the only major key that carries all seven. On the page Circle of fifths it appears with “7 sharps” at the end of the sharp series. The rule for the tonic applies here too: the tonic lies a semitone above the last sharp, so above B♯, and that is C♯.

C♯ major scale

C♯ D♯ E♯ F♯ G♯ A♯ B♯ C♯ 1 1 ½ 1 1 1 ½

All seven degrees carry a sharp. E♯ and B♯ are marked: they sound like F and C, but are written this way so that every letter occurs once.

DegreeC♯ majorD♭ major
1C♯D♭
2D♯E♭
3E♯F
4F♯G♭
5G♯A♭
6A♯B♭
7B♯C
Key signature7 ♯5 ♭

C♯ major or D♭ major?

C♯ major and D♭ major are an enharmonic pair. The Circle of Fifths page names the rule: composers choose, wherever possible, the spelling with fewer sharps or flats, because it is easier for musicians to read. D♭ major with five flats is almost always preferred to C♯ major with seven sharps, although both sound identical on the piano. See Enharmonic equivalence.

The exercise page on enharmonics describes a trap: if a D♭ major chord appears in a lead sheet and the student fingers C♯ major, everything sounds right, but the next line suddenly no longer fits the score.

The chords

The diatonic chords arise as in every major key from two stacked thirds: the degrees I, IV and V carry major chords, here C♯, F♯ and G♯, ii, iii and vi carry minor chords and the seventh degree a diminished triad. The derivation is on the page Diatonic chords.

C♯IF♯IVG♯VC♯I
Try it yourself: On higher levels the training Key Signatures shows all seven sharp and seven flat keys. In Name the Note you practise thirds in difficult keys such as D♭ major and F♯ major.

Common mistakes

  • Writing E♯ and B♯ as F and C: In C♯ major the notes are called E♯ and B♯, otherwise a letter occurs twice.
  • Equating C♯ major and D♭ major: On the piano they sound the same, in notation they belong to different key series: C♯ major to the sharp keys, D♭ major to the flat keys.
  • Swapping the order of the sharps: F♯, C♯, G♯, D♯, A♯, E♯, B♯.

Continue on Maikstrings

Circle of fifths

C♯ major at the end of the sharp series and the enharmonic equivalence with D♭ major.

Key Signatures

Recognise all seven sharp keys, up to C♯ major.

Enharmonic Matching

C♯ and D♭: the same note with two names.

Related terms

D♭ majorF♯ majorEnharmonic equivalenceSharp keyRelative keyMajorCircle of fifthsAccidentalKey

Editor: Maik Krohm · reviewed on 3 October 2026

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