Circle of Fifths
Select a key
Scales & modes
1 · 2 · 3 · 4 · 5 · 6 · 7
G Ionian (Major)
Intervals
Shapes can be moved across the entire fretboard.
👆 Click an interval above to see how to play it on guitar.
Triads
G · A · B · C · D · E · F♯
Chord library
Shapes, voicings and scales to solo over the chord.
Click a diagram to hear it. The chord also shows on the fretboard (chord tones, tensions, avoid notes).
Chord progressions
Diatonic chords of the current key — click to hear them.
Chords from parallel scales with the same tonic — e.g. iv and ♭VI from minor in a major key. They sound colorful but resolve naturally to the tonic.
Progression editor
Build your own progression: bars, meter, tempo, up to 4 chords per bar.
Click a chord to edit it (it also shows on the fretboard and circle). With nothing selected, “Insert chord” adds a new bar.
Frequently Asked Questions
Guitar theory, scales and the fretboard — explained.
What is the circle of fifths and how do I use it?
The circle of fifths arranges all 12 keys by perfect fifths. Moving clockwise adds a sharp; counter-clockwise adds a flat. It shows key signatures, relative minor keys and which chords belong together, making it the fastest way to understand key relationships and write chord progressions on guitar.
How does the CAGED system work on guitar?
CAGED breaks the fretboard into five movable shapes — based on the open C, A, G, E and D chords — that interlock across the neck. Each shape covers one position of a scale or chord, so learning all five lets you play any key anywhere on the guitar.
What are the seven guitar modes?
The modes of the major scale are Ionian (major), Dorian, Phrygian, Lydian, Mixolydian, Aeolian (natural minor) and Locrian. Each starts on a different scale degree and has its own characteristic notes and mood, from the bright Lydian to the dark Phrygian.
What is the difference between CAGED and 3-notes-per-string?
CAGED uses five boxy positions with two or three notes per string, ideal for chords and visualization. The 3-notes-per-string (3NPS) system uses seven positions with exactly three notes on every string, which is faster for legato and lead playing. Both cover the same scale.
How do I memorize the guitar fretboard?
Start with the natural notes on the low E and A strings, learn the octave shapes, then connect notes through scale positions and the CAGED shapes. Visualizing intervals and root notes — as in FretboardMentor — turns rote memorization into fast pattern recognition.
What are intervals on the guitar?
An interval is the distance between two notes measured in semitones — for example a minor third (3 semitones) or a perfect fifth (7). Learning interval shapes lets you build any scale, chord or arpeggio anywhere on the neck.
What are triads and chord inversions?
A triad is a three-note chord built from a root, third and fifth. Major, minor, diminished and augmented triads differ by their third and fifth. Inversions reorder those notes so a different tone sits in the bass, giving compact chord voicings across string sets.
Is FretboardMentor free to use?
Yes. FretboardMentor is completely free, runs in your browser with no sign-up, and supports any key in standard tuning, with light and dark themes and full English and Polish interfaces.