Read a key signature off the staff and name the major and minor key — or work the other way and give the number of sharps or flats. Instant feedback and a running score.
A key signature is the block of sharps or flats at the start of every staff. It tells you which notes are altered for the whole piece, so you do not have to mark every accidental individually. There are fifteen of them — seven sharp keys, seven flat keys, and C major with no accidentals at all.
Sharps are always added in the order F C G D A E B. Flats are always added in the exact reverse: B E A D G C F. Each sits in a fixed spot on the staff, so after a little drilling you recognise a signature by its shape before you have counted anything.
For sharp keys, the major key is one semitone above the last sharp. For flat keys, the major key is the name of the second-to-last flat (the exception is one flat, which is F major). The relative minor is always a minor third below the major — A minor for C major, E minor for G major, and so on.
| Sharp keys | Flat keys |
|---|---|
| G · D · A · E · B · F♯ · C♯ | F · B♭ · E♭ · A♭ · D♭ · G♭ · C♭ |
Once the signatures are automatic, see how the keys relate around the Circle of Fifths, drill the notes themselves with the Sight-Reading Trainer, or follow the full Music Theory Fundamentals path.
1. Pick a mode: Name the key (read the signature, answer the key) or Count the accidentals (see a key, answer how many sharps or flats).
2. Choose the range — up to 3 sharps or flats while learning, all 15 keys once they feel familiar.
3. Press Start, answer, and use the instant feedback and running score to see which keys still slow you down.
The staff shows three sharps: F♯, C♯, G♯. The last sharp is G♯ and the major key is a semitone above it — A major. Its relative minor is three semitones lower: F♯ minor. With four flats — B♭ E♭ A♭ D♭ — the second-to-last flat is A♭, so the key is A♭ major, with F minor as its relative minor.
How do you read a key signature?
Count the sharps or flats and use the order they always appear in. Sharps go F C G D A E B;
the key is one semitone above the last sharp. Flats go B E A D G C F; the key is the
second-to-last flat (except one flat, which is F). Every major key shares its signature with
a relative minor a minor third below.
What is the order of sharps and flats?
Sharps are added in the order F, C, G, D, A, E, B. Flats are added in the reverse order: B,
E, A, D, G, C, F. Each is always written in the same position on the staff, which is why the
shape of a key signature is instantly recognisable once you have drilled it.
Is this key signature trainer free?
Yes, completely free with no account and no ads. It runs entirely in your browser and works
offline once the page has loaded.
What is a relative minor?
Every major key shares its key signature with the minor key three semitones below it: C
major and A minor have no sharps or flats, G major and E minor have one sharp. The signature
alone cannot tell them apart — the music's home chord does.
Why are there 15 key signatures and not 12?
Three keys can be spelled two ways: B major (5 sharps) is also C♭ major (7 flats), F♯ major
(6 sharps) is also G♭ major (6 flats), and C♯ major (7 sharps) is also D♭ major (5 flats).
Twelve pitches, fifteen spellings.