Nashville Number System

Chord Decoder

Type the chords in a song. We'll find the key and label each chord with its Nashville number — showing the steps along the way.

Try an example

Detected Key

C Major

1

Find the two Major chords adjacent in the alphabet

In the key of C, those are F and G — your 4 and 5.

4

F

Major

5

G

Major

2

The remaining Major chord is your 1

C is the only Major left — it's the tonic, the home chord of the key.

1

C

Tonic

3

Fill in the rest by following the alphabet

Minors get the in-between numbers (2, 3, 6), and the diminished is always 7.

6

Am

minor

Full Number Map

Key of C

1

C

Major

2

—

3

—

4

F

Major

5

G

Major

6

Am

minor

7

—

The Method

How to Turn Chords Into Numbers

Every major key has the same pattern of chord qualities across its seven scale degrees:

1

2

3

4

5

6

7

MajorminorminorMajorMajorminordim
  1. Find 4 and 5. Look at the chords in your song. Find the two Major chords whose root notes are right next to each other in the musical alphabet (A, B, C, D, E, F, G — then wrapping back to A). Those two are your 4 and 5.
  2. Find 1. The remaining Major chord — the one not part of that pair — is your 1. The key of the song takes its name from this chord.
  3. Fill in the rest by alphabet. The minors (2, 3, 6) and the diminished (7) fall into place by continuing alphabetically. Each step up the alphabet is the next number.

Heads-up

The musical alphabet has only seven letters — A B C D E F G — then it starts over. Sharps (#) and flats (♭) ride along with whichever letter they're attached to.