Key Signature Calculator — Major & Minor Keys
Select sharps or flats and the count to instantly identify the major key, its relative minor, and the exact accidentals in that key signature.
Accidental type
Number of accidentals
How does this calculator work?
Choose sharps or flats and count (0–7) to get the major key, relative minor, and specific accidentals. Sharps follow F C G D A E B; flats follow B E A D G C F. Each additional accidental moves one perfect fifth around the circle. 0 = C major / A minor; 1 sharp = G major / E minor; 1 flat = F major / D minor.
Formula
How this is calculated
A key signature tells a musician which notes are permanently raised (sharp) or lowered (flat) throughout a piece, so the composer does not need to mark every individual note. Western music organises its 12 major keys around the circle of fifths — a sequence where each adjacent key differs by exactly one accidental.
Sharps are added in a fixed order: F♯, C♯, G♯, D♯, A♯, E♯, B♯ (mnemonic: "Father Charles Goes Down And Ends Battle"). Each new sharp moves the key up a perfect fifth. To identify a sharp key from notation: look at the last sharp and go up one semitone — that is the tonic. For flat keys, the order is B♭, E♭, A♭, D♭, G♭, C♭, F♭ ("Battle Ends And Down Goes Charles Father"). For flats, the major key is named after the second-to-last flat (exception: 1 flat = F major, memorised directly).
Every major key shares its key signature with a relative minor that starts a minor third (three semitones) below the major tonic, giving the same set of notes a different tonal centre. The number line shows each key's position on the circle of fifths — sharps to the right, flats to the left, C major at the centre.
Frequently asked questions
For sharps: name the last sharp (e.g., D♯) and go up one semitone → E major. For flats: name the second-to-last flat (e.g., E♭ in a 3-flat signature) → E♭ major. Exception: 1 flat always = F major.
Every major key has a relative minor that uses exactly the same key signature (same sharps/flats) but centres on the sixth scale degree — three semitones below the major tonic. A minor is relative to C major; E minor is relative to G major; and so on.
Western equal-tempered music has 12 distinct pitches per octave. Beyond 7 accidentals the key names require double accidentals and are enharmonically equivalent to simpler keys on the other side of the circle. Most notation stops at 7 because C♯ major = D♭ major (enharmonic), F♯ major = G♭ major, and so on.
Also known as
TG we-Calculate Editorial Team. (2026). Key Signature Calculator — Major & Minor Keys [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/key-signature-calculator
TG we-Calculate Editorial Team. "Key Signature Calculator — Major & Minor Keys." TG we-Calculate. 2026. https://we-calculate.com/calculator/key-signature-calculator.
TG we-Calculate Editorial Team, "Key Signature Calculator — Major & Minor Keys," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/key-signature-calculator
@misc{wecalculate_key_signature_calculator, title = {Key Signature Calculator — Major & Minor Keys}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/key-signature-calculator}}, year = {2026}, note = {TG we-Calculate} }
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