Roman Numeral Analysis

Roman numeral analysis names a chord by its scale-degree role — I, ii, V — instead of its absolute letter name. That single move is why it exists: Dm7–G7–Cmaj7 and Fm7–B♭7–E♭maj7 are the exact same progression, a ii–V–I, just heard in two different keys. Once you can hear “a ii–V–I” instead of memorizing twelve unrelated sets of chord symbols, you can transpose on the fly, spot patterns across hundreds of tunes, and talk about harmony with other musicians in a language that survives any key change.

The same iim7–V7–Imaj7 shape, transposed:

What the numerals encode

Each numeral marks a scale degree of the key (built from The Major Scale or its minor relatives, per Scale Degrees), and its case plus quality suffix tells you the chord itself. Uppercase means a major triad, lowercase means minor, and a degree symbol or “ø” marks diminished — a seventh chord just tacks the quality onto the numeral, so Cmaj7 in C is Imaj7 and Dm7 is iim7. You’ll also see a competing jazz-lead-sheet convention that keeps everything uppercase and lets the suffix do all the work (IIm7, V7, Imaj7); neither is wrong, but stay consistent within one analysis, and note this differs from the classical figured-bass tradition (I⁶, I⁶₄) that also tracks inversions, which jazz numerals generally ignore.

The diatonic ladder in major

Stacking thirds on every degree of a major scale gives you seven seventh chords, and this table is worth memorizing cold — it’s the backbone of Diatonic Harmony:

Arpeggiated in C, the ladder sounds like this:

Everything about Functional Harmony flows from this table: I and vi feel like home, ii and IV feel like motion away from home, and V pulls hard back to I. Learn it once, in any key via Transposition, and it works everywhere.

Chromatic numerals and borrowed chords

Not every chord in a tune comes straight off the major scale, and numerals handle that with accidentals rather than throwing out the system. A ♭VII7 (B♭7 in the key of C) is a common blues-inflected chord; a chord borrowed from the parallel minor, like ♭VImaj7 or iv, is Modal Interchange and still gets a numeral, just with a flat to flag where it came from. The most important chromatic move, though, is the secondary dominant — a V7 that resolves not to the tonic but to some other diatonic chord, written V7/ii (A7 in C, resolving to Dm7) or V7/V (D7 in C, resolving to G7). Chain enough of these together and you get the extended ii–V motion that drives most jazz reharmonization and Turnarounds.

Reading a real tune: Autumn Leaves

Autumn Leaves is the textbook case for why numerals matter more than chord names, because its opening bars pivot between a relative major and minor key under one shared key signature:

• Cm7 – F7 – B♭maj7 – E♭maj7 → ii7 – V7 – Imaj7 – IVmaj7 in B♭ major
• Am7♭5 – D7 – Gm → iiø7 – V7 – i in G minor

Both cadences share one key signature (two flats), so the pivot is purely harmonic, not notational:

That’s analyzing with numerals in a nutshell: the same four measures that look like an unrelated string of chord symbols reveal themselves as two textbook cadences, a major-key ii–V–I sliding into a minor ii–V–i, because Roman numerals track function through the key change instead of getting distracted by the letter names on the lead sheet. The same logic extends to full Minor Key Harmony, where the v chord is often raised to V to get a proper dominant pull into the tonic.

♫ Listen

• Bill Evans Trio — “Autumn Leaves” (Portrait in Jazz, 1959): Evans’s comping makes the B♭-major ii–V–I and the G-minor ii–V–i sound like two distinct rooms in the same house — listen for the shift in color right at the pivot chord.
• Cannonball Adderley & Miles Davis — “Autumn Leaves” (Somethin’ Else, 1958): the melody itself traces the ii–V–I so plainly that you can sing the numerals along with Davis’s muted trumpet.
• John Coltrane — “Giant Steps” (Giant Steps, 1960): not a standard, but built entirely from cycling ii–V–I cells in three keys a major third apart — proof that once you truly hear the numerals, you can follow harmony moving at any speed.

Related: Functional Harmony, Diatonic Harmony, Secondary Dominants, Chord Symbols