Key Detector
Identify the musical key of any chord progression. Understand which key your chords belong to and why — no automatic detector needed, just four reliable methods below.
Get an instant key suggestion in Chord Player
Add your chords in Chord Player and switch to the Roman Numeral view — it shows the most likely key for your progression in one click, faster than working it out by hand.
Open free Chord PlayerHow to find the key of a chord progression
The key of a chord progression is determined by the tonal center — the chord that feels like "home." Here are the most reliable methods:
Check for a V7 chord
A dominant 7th chord (e.g. G7) almost always resolves to its I chord (Cmaj7). If you have G7 → C, the key is C major.
Find all the diatonic chords
List the chords and find the major scale that contains all of them. For C, G, Am, F — all four fit perfectly into C major (I, V, VI, IV).
Listen for the resting chord
The chord where the progression feels resolved or complete is usually the I (tonic). Play the progression and notice where it "wants to land."
Check relative minor
C major and A minor share the same chords. A progression starting on Am and ending on Am is likely in A minor. Starting on C and ending on C is likely C major.
Examples — hear the key
All chords are diatonic to C major. The I chord (C) is the tonal center.
Starts on Am — feels like A minor. Same notes, different tonal center.
II–V–I in C. The G7 resolves strongly to Cmaj7, confirming C as the key.
Frequently asked questions
Is there an automatic key detector tool?
Not a standalone one on this page — but Chord Player's Roman Numeral view analyzes the chords you enter and suggests the most likely key automatically, which is the fastest option if you don't want to work it out by hand.
How do I find the key of a song without any tools?
Look for a V7 → I resolution (a dominant seventh chord resolving to a major chord one fourth above it) — that almost always confirms the key. If there's no clear dominant chord, list every chord you hear and find the one major scale that contains all of them; the "home" chord in that scale is your key.
How can the same four chords be two different keys?
Every major key shares its exact chords with its relative minor — C major and A minor both use C, Dm, Em, F, G, Am, and Bdim. The chords alone don't tell you which key you're in; what matters is which chord the progression resolves to and starts/ends on. Am–F–C–G feels like A minor; C–G–Am–F feels like C major.
Does the key affect which chords I can use next?
Yes — once you know the key, its diatonic chords (the ones built from that key's scale) are the ones most likely to sound "in key." The Circle of Fifths tool shows you all seven diatonic chords for any key at a glance.