To find what key you are in with a capo, add the capo fret to the chord shape: a C shape with a capo on the 2nd fret sounds as D major, because C plus two semitones is D, and a G shape with a capo on the 3rd fret sounds as Bb major, because G plus three semitones is Bb.
What key am I in with a capo?
To find what key you are in with a capo, add the capo fret to the chord shape: the shape tells you the starting note, and the capo fret tells you how many semitones to add. A C shape with a capo on the 2nd fret sounds as D major, because C plus two semitones is D. A G shape with a capo on the 3rd fret sounds as Bb major, because G plus three semitones is Bb. A D shape with a capo on the 5th fret sounds as G major, because D plus five semitones is G. The shape is the starting point, and the capo fret is the distance. The question matters because guitarists often play with a capo and need to tell other musicians what key they are in. A guitarist who says I am playing in C shapes with a capo on the 2nd fret is playing in D major, and the bass player, the pianist and the singer need to know that, or they will play in the wrong key. The capo key is the sounding key, the key the listener hears, and it is different from the shape key, the key the guitarist's fingers are playing. The capo calculator works out the sounding key for any shape and any fret.
How to work out the capo key
The method is to count semitones from the shape. A capo on fret n raises every note by n semitones, so the sounding chord is the shape chord transposed up by n semitones. A C shape at the 1st fret is C# major, at the 2nd fret is D major, at the 3rd fret is Eb major, at the 4th fret is E major, at the 5th fret is F major, and at the 7th fret is G major. A G shape at the 1st fret is Ab major, at the 2nd fret is A major, at the 3rd fret is Bb major, at the 5th fret is C major, and at the 7th fret is D major. The same maths works for minor shapes: an Am shape at the 2nd fret sounds as Bm, because A plus two semitones is B, and an Em shape at the 3rd fret sounds as Gm, because E plus three semitones is G. To find the key of a whole song with a capo, work out the sounding key of the I chord, which is the chord the song is built around. If the song uses C shapes with a capo on the 2nd fret, the I chord sounds as D major, so the song is in D major, and the other chords follow: the F shape sounds as G major, the IV chord of D major, and the G shape sounds as A major, the V chord of D major. The key of D major lists the chords of the sounding key, and the capo chart shows the sounding chord for any shape and any fret.
Worked example — a song in G shapes with a capo on the 5th fret. The I chord is a G shape, and G plus five semitones is C, so the song is in C major. The IV chord is a C shape, and C plus five semitones is F, which is the IV chord of C major. The V chord is a D shape, and D plus five semitones is G, which is the V chord of C major. The vi chord is an Em shape, and E plus five semitones is A, so the vi chord sounds as Am, which is the vi chord of C major. The whole song is in C major, even though the guitarist is playing G shapes, and the key of C major lists the sounding chords.
How to practise finding the capo key
Practise by naming the sounding key before you play, so the calculation becomes automatic and you can tell other musicians the key without hesitating.
- Play a C shape with a capo on the 3rd fret, and name the sounding chord, Eb major, before you check it against the capo chart.
- Play the I–V–vi–IV progression in C major with a capo on the 2nd fret, and name the sounding key, D major, before you play it.
- Take a song in G shapes with a capo on the 5th fret, and work out the sounding key, C major, by adding five semitones to the G shape.
- Practise with minor shapes: play an Am shape with a capo on the 2nd fret, and name the sounding chord, Bm, before you check it.
- Use the capo calculator to check your answers, and repeat the exercise until you can work out the sounding key in seconds.
Common mistakes
- Telling other musicians the shape key — If you are playing C shapes with a capo on the 2nd fret, you are in D major, not C major, and telling the band you are in C major will make them play in the wrong key. Always give the sounding key, not the shape key.
- Forgetting that the capo raises minor chords too — A capo raises every chord by the same interval, major or minor. An Am shape at the 2nd fret sounds as Bm, not as B major, because the minor quality follows the shape, and only the root moves.
- Counting the capo fret wrong — A capo on the 2nd fret raises the pitch by two semitones, not by two whole tones. Count semitones, one per fret, or the sounding key will be wrong by a whole tone or more.
Quick reference
This table shows the sounding chord for six common shapes at three capo frets, so you can see the addition working in every row: the shape plus the fret equals the sounding chord, and the maths is one semitone per fret, every time.
| Shape played | Capo fret | Sounding chord |
|---|---|---|
| C shape | 2nd fret | D major |
| C shape | 3rd fret | Eb major |
| G shape | 2nd fret | A major |
| G shape | 5th fret | C major |
| D shape | 5th fret | G major |
| E shape | 1st fret | F major |
| A shape | 5th fret | D major |
| Am shape | 2nd fret | Bm |
| Em shape | 3rd fret | Gm |
Use the table as a quick reference when you play with a capo, and test yourself by covering the third column and working out the sounding chord from the shape and the fret. When you can do that without looking, you can tell any musician the key you are in, without hesitating and without a chart.
Frequently asked questions
What key am I in with a capo?
Add the capo fret to the chord shape: a C shape with a capo on the 2nd fret sounds as D major, because C plus two semitones is D, and a G shape with a capo on the 3rd fret sounds as Bb major, because G plus three semitones is Bb.
How do I tell other musicians what key I am in?
Give the sounding key, the key the listener hears, not the shape key, the key your fingers are playing. If you are playing C shapes with a capo on the 2nd fret, tell the band you are in D major.
Does a capo change the key of every chord?
Yes. A capo raises every chord by the same interval, so the whole song moves up together. If the I chord moves from C to D, the V chord moves from G to A, and the vi chord moves from Am to Bm, by the same two semitones.
Can I work out the capo key without a chart?
Yes, by counting semitones: add the capo fret to the shape chord, one semitone per fret. A D shape at the 5th fret is D plus five semitones, which is G major, and the chart is just a shortcut for that calculation.
What if I use a capo on the 7th fret?
The maths is the same: add seven semitones, a perfect 5th, to the shape. A C shape at the 7th fret sounds as G major, a G shape sounds as D major, and a D shape sounds as A major.