π Song Key Finder
Enter a song's chords and discover its most likely key, ranked by confidence.
Most likely key
Tip: include the verse and chorus chords together for the most reliable result. Qualities like m, 7, and dim are understood.
How to Use This Key Finder
Type or paste the chords of the song into the box, separated by commas, spaces, or line breaks, and the finder instantly scores every major and minor key against your chords. The key with the most matching diatonic chords appears at the top with a confidence percentage, followed by the next closest candidates, the full set of diatonic chords for the winning key, and any of your chords that fall outside it.
Enter the song's chords in playing order, for example: G, C, D, Em. Include both the verse and the chorus if you know them; more chords mean a more reliable answer.
Read the top result: the key name and its confidence score. 100 percent means every chord you entered belongs naturally to that key.
Check the ranked list below. If the top two keys are close, listen for which tonic chord the song resolves to at the end of phrases; that resolution is the tiebreaker no algorithm can replace.
Note any flagged non-diatonic chords. These are the song's color chords (borrowed chords, secondary dominants), and knowing them helps you solo and arrange over the song correctly.
How Key Detection Works
Every key owns a fixed family of seven diatonic chords, and songs overwhelmingly draw from their home key's family. The finder builds all 24 families (12 major, 12 minor) and counts, for each one, how many of your input chords appear in it. Chord quality matters: Dm counts as diatonic in C major, but D major does not. For minor keys the finder accepts both the natural minor v chord and the raised major V chord from harmonic minor, since that major V appears in the majority of minor-key songs.
Ties and near-ties are musically meaningful, not errors. Keys a fifth apart share six of seven chords, and relative major/minor pairs share the same pitch collection entirely. When C major and A minor tie, the music itself decides: if phrases resolve to C, the song is in C major; if they resolve to Am, it is in A minor. The confidence score tells you how clean the fit is, and anything above 75 percent with four or more chords is usually decisive.
Worked Example
Enter G, C, D, Em. In G major, the diatonic chords are G, Am, Bm, C, D, Em, F#dim, so all four input chords fit: confidence 100 percent, and G major ranks first. C major scores 75 percent (G, C, Em fit, but D major is not diatonic to C), and E minor scores 100 percent as well since it shares G major's chords. The tiebreaker is musical: the progression starts and ends on G, so G major is the answer.
Try a trickier one: Am, F, C, G. A minor's family (Am, Bdim, C, Dm, Em, E, F, G) contains all four, giving A minor 100 percent. C major also scores 100 percent on pitch content. Here the resolution decides again: this is the classic sensitive progression that most ears hear resolving to Am, so A minor wins on musical grounds even though the numbers tie.
Practical Tips
Once you know the key, the finder shows you the key's full diatonic chord family, which is your roadmap for the song. Soloists can lean on the key's pentatonic scale, arrangers can predict which chords the bridge probably uses, and transposers can convert the whole song with our Nashville Number Chart Generator. Pay special attention to flagged non-diatonic chords: a b7 chord suggests Mixolydian flavor, a major II chord is usually a secondary dominant heading to V, and a minor iv in a major key is the classic borrowed chord of countless ballads.
If the confidence is low across the board, the song may modulate (change keys mid-song, common in bridges), or it may be blues-based, where dominant seventh chords on I, IV, and V deliberately break diatonic rules. In that case, analyze the verse and chorus separately. And remember the golden rule of key finding: the last chord of the song is the tonic more often than not, so weight the ending heavily when the scores are close.
Frequently Asked Questions
How does this tool find the key of a song?
It tests your chords against all 12 major and all 12 minor keys and counts how many of your chords are diatonic, meaning built naturally from that key's scale. The key where the most chords fit wins. The confidence percentage tells you how clean the fit is: 100 percent means every chord belongs to the key.
What does diatonic mean?
Diatonic chords are the seven chords built from the notes of a key's scale with no outside notes. In C major they are C, Dm, Em, F, G, Am, and Bdim. When most of a song's chords are diatonic to one key, that key is almost certainly the song's home key.
Why do I get several keys with high scores?
Closely related keys share most of their chords. C major, G major, and F major share five of seven diatonic chords, and C major shares all its pitch content with A minor. Look at the top result first, then check which key's tonic chord the song actually resolves to at the end of phrases.
What if some chords do not fit any key?
Those are chromatic or borrowed chords, and they are completely normal. Rock and pop songs constantly borrow the b7 chord, secondary dominants like the V of V, or the minor iv chord. The tool flags non-diatonic chords for the top key so you can spot the song's color chords instead of treating them as errors.
Does this work for minor keys too?
Yes. All 12 minor keys are scored alongside the majors, using both the natural minor chords and the raised major V chord from harmonic minor, which is extremely common in real songs. If your progression centers on a minor tonic like Am with an E major chord in it, A minor will rank at the top.
How many chords do I need for a reliable result?
Three or four chords usually point clearly to one key, and a full verse plus chorus of six to eight chords is very reliable. With only one or two chords the tool can only narrow it to a few candidates, since two chords can belong to several keys at once.