The song key finder identifies the most likely musical key from a list of chord names. Enter the chords from a song (separated by commas) to see which key they belong to and each chord's function in that key.
Enter Chords
Use: C, Cm, C7, Cmaj7, Csus2, Csus4, Caug, Cdim. Minor: use lowercase m (Am, Dm, Em).
How to Find the Key of a Song
The key of a song defines which scale the melody and harmony are built from. Most Western music uses major or minor keys, and identifying the key helps you transpose, improvise, and understand chord relationships.
How the Algorithm Works
The key finder checks each of the 24 common major and minor keys (12 major, 12 minor) to see how many of your input chords belong to each key's diatonic chord set. The key with the most matching chords is shown first. When multiple keys have the same score, relative major/minor pairs are shown together.
Common Chord Progressions and Their Keys
I-V-vi-IV (C-G-Am-F) is C major. i-VII-VI-VII (Am-G-F-G) is A minor. I-IV-V (G-C-D) is G major. The I chord typically starts and ends the progression and sounds resolved. If you're unsure, play each candidate key's I chord — the one that sounds like "home" is the correct key.
FAQ
Is this song key finder free?
Yes, completely free with no signup required.
How do I find what key a song is in?
The key is determined by which major or minor scale contains all (or most) of the chords in the song. The tonic chord (I) usually appears at the beginning or end and sounds like 'home.' The V chord (dominant) creates tension that resolves to I. Enter all the chords and look for a key where they all fit naturally.
What does I, IV, V mean in music?
Roman numerals represent chord functions within a key. I (tonic) is home — stable and resolved. IV (subdominant) moves away from home. V (dominant) creates tension that wants to resolve to I. In C major: C=I, F=IV, G=V. These three chords form the basis of most folk, blues, and rock progressions.
What is a relative minor?
Every major key has a relative minor that shares the same notes. C major's relative minor is A minor — both use only the white keys on a piano. A song can borrow chords from its relative minor to add color. Many songs shift between a major key and its relative minor.
What if the chords don't fit any key perfectly?
Songs often borrow chords from related keys (modal mixture). A I-IV-bVII-I progression in C major borrows Bb (bVII) from C mixolydian mode. Secondary dominants (like E7 in C major going to Am) add color. The key finder shows the best-fit key even if not all chords match exactly.