Chord Structure · Lesson 4
Roman Numeral Analysis in Major and Minor
about 15 min
What this lesson is for
Roman numerals name chords by scale degree instead of by letter, so one description covers every key at once. This lesson sorts out upper and lower case, the added inversion figures, and the conventions that apply specifically in minor keys.
- Explain that Roman numerals are degree-based and therefore key-independent
- Use upper case, lower case, and the symbols ° ø + correctly
- Write the Roman numerals for the diatonic chords of major and minor keys
- Explain why the raised leading tone in minor takes no accidental in the numeral
In this lesson
Chords have been named by letter so far — C, Am, G7. That notation has one decisive weakness: change the key and every symbol has to be rewritten.
The progression C–Am–F–G and the progression D–Bm–G–A are the same progression. Only the key differs; the sequence of roles the chords play is identical. Roman numerals are the notation that can express that identity.
Naming chords by degree
A Roman numeral identifies a chord by which degree of the scale its root sits on.
Write “I–vi–IV–V” and you have described a progression that holds in every key. In C major it is C–Am–F–G; in D major, D–Bm–G–A; in E-flat major, E♭–Cm–A♭–B♭. One notation covers all of them.
Same numerals, different keys
Check: Both are I–vi–IV–V. Not one letter name is shared between them, and yet the sequence of roles is identical, so they register as the same progression. That shared identity is exactly what Roman numerals capture.
C–Am–F–G
Case and symbols
In the classical system, the appearance of the numeral itself reports the chord quality.
| Chord type | Notation | Example |
|---|---|---|
| Major triad | upper case | I, IV, V |
| Minor triad | lower case | ii, iii, vi |
| Diminished triad | lower case + ° | vii° |
| Augmented triad | upper case + + | III+ |
| Major seventh | upper case + M7 | IM7, IVM7 |
| Dominant seventh | upper case + 7 | V7 |
| Minor seventh | lower case + 7 | ii7, vi7 |
| Half-diminished seventh | lower case + ø7 | viiø7 |
| Diminished seventh | lower case + °7 | vii°7 |
The elegance of this design is that quality is legible from the symbol alone. See “ii” and you know it is minor; see “V” and you know it is major. No annotation required.
Popular-music writing uses different conventions. One common approach keeps Roman numerals but marks minor chords with an m and leaves the case uniform (I, IIm, V7) — that is the style this site’s tools output. The Nashville Number System goes further and uses Arabic numerals (1, 6m, 4, 5) so that charts can be written and transposed at speed. None of these is more correct than the others; they are conventions belonging to different fields. The next lesson sets out how they correspond.
Check
How is Am7 in C major written as a classical Roman numeral?
Adding inversion figures
The figured bass numbers from the previous lesson attach directly to the numeral.
| Position | Triad | Seventh chord |
|---|---|---|
| Root position | I | V7 |
| First inversion | I6 | V65 |
| Second inversion | I64 | V43 |
| Third inversion | — | V42 |
To restate the principle: inversion does not change the degree. V6 and V64 are both the V chord. The root’s degree fixes the chord’s identity, and the inversion figure records only its arrangement.
Roman numerals in minor
Minor keys are slightly more involved, because the seventh degree is variable — natural or raised.
Degrees are counted against natural minor, and then upper or lower case is chosen according to the quality of the chord that actually sounds.
The diatonic triads of C harmonic minor come out as follows.
Compared with major, the pattern differs in several places:
- V is upper case, because the raised seventh makes it major
- III+ is augmented, because it contains the raised seventh
- vii° is diminished, standing on the leading tone
The leading tone takes no accidental
There is a convention here. C minor has three flats, so its seventh degree is properly B♭. The chord standing on the raised B looks, in degree terms, like it should be ♯VII.
It is nonetheless written vii°, with no sharp.
The reason is that in minor keys, harmonic minor is presupposed as the harmonic standard. Raising the leading tone is not an event that needs announcing; it is the default state of affairs.
Conversely, the major triad built on the natural seventh degree (B♭) is written VII, with no flat. B♭ is the seventh degree of natural minor — the reference against which degrees are counted — so nothing has been altered.
This is a common source of confusion, so it is worth tabulating. The standard is that Roman numerals in minor count degrees against natural minor. Therefore:
| Chord (in C minor) | Roman numeral | Reason |
|---|---|---|
| B♭ (major triad) | VII | the natural minor seventh degree itself |
| B (diminished triad) | vii° | the raised seventh; convention omits the sharp |
| A♭ (major triad) | VI | the natural minor sixth degree itself |
| E♭ (major triad) | III | the natural minor third degree itself |
The same B♭ chord is ♭VII in C major, because there the seventh degree is B and B♭ genuinely is lowered. Whether the flat appears depends on the key, not on the chord.
Popular-music sources do sometimes write ♭VII in minor keys as well, since “the ♭VII chord” has become a fixed name across both modes. The notation genuinely varies, so when reading, check which reference the writer is counting from. This site’s tools follow the natural-minor reference in the table above.
Telling v from V in minor
Check: The first uses the natural seventh degree, giving v (Gm) into i. The second uses the raised seventh, giving V (G) into i. Roman numerals write these as lower-case v and upper-case V respectively — check that the case corresponds precisely to what you hear.
Gm → Cm. Lower-case v
Check
How is the major triad on B♭ in C minor written as a classical Roman numeral?
Check
How is the major triad on A♭ in C major written as a classical Roman numeral?
Altered chords take a prefixed accidental
Chords from outside the key put an accidental in front of the numeral.
| Chord (in C major) | Roman numeral | Category |
|---|---|---|
| A♭ | ♭VI | borrowed from the parallel minor |
| E♭ | ♭III | borrowed |
| B♭ | ♭VII | borrowed |
| D7 | II7 (= V7/V) | secondary dominant |
| F♯dim | ♯iv° | passing |
The degree is determined by the letter distance in the note name. A♭ in C major is ♭VI because A is the sixth degree — never ♯V. The Unit 0 principle that letters determine degrees continues to govern harmonic analysis unchanged.
Unit 8 treats these altered chords from a functional standpoint. At this stage it is enough to be able to write them correctly.
Look at the diatonic chords with their degree labels Change the key and confirm that the sequence of degrees does not change. That invariance is precisely the abstraction Roman numerals capture Diatonic Chord Reference → Enter a progression and have it analyzed by degree Type something like C Am F G and it will infer the key and report degrees and functions. Do your own analysis first and compare Chord Progression Analyzer →Exercises
Every answer here is cross-checked against the theory engine. Work them out before you grade.
- 1
Write the seven diatonic triads of C major as classical Roman numerals, in order, separated by single spaces.
- 2
Write the seven diatonic seventh chords of C major as classical Roman numerals, in order, separated by single spaces.
- 3
Write the seven diatonic triads of C harmonic minor as classical Roman numerals, in order, separated by single spaces.
- 4
How do you write the first inversion of the G chord (V in C major) as a Roman numeral?
- 5
Why is the chord on the raised seventh degree in minor (Bdim in C minor) written vii° rather than with a sharp?
Before you move on
Check that you can explain each point above in your own words.