# Roman numerals

*Module 8 · Lesson 2: Harmony in a key · BazzLow*

> Name chords by their degree with Roman numerals so a progression works in any key.

Before this lesson: [8.1 Diatonic triads](https://bazzlow.com/en/harmony-in-a-key/diatonic-triads/)

Chord names change with the key. Numbers do not. Roman numerals let you write a progression once and play it in any key.

## Numbering the chords

Chords are numbered with **Roman numerals** on the degree of their root. The numeral also shows the quality:

- **UPPERCASE** = major (I, IV, V);
- **lowercase** = minor (ii, iii, vi);
- **lowercase + °** = diminished (vii°);
- **uppercase + “+”** = augmented (III+).

In a major key the chords are **I – ii – iii – IV – V – vi – vii°**.

*The numerals I to vii° and the chords they name in five keys.*

| Key | I | ii | iii | IV | V | vi | vii° |
| --- | --- | --- | --- | --- | --- | --- | --- |
| C | C | Dm | Em | F | G | Am | B° |
| G | G | Am | Bm | C | D | Em | F♯° |
| D | D | Em | F♯m | G | A | Bm | C♯° |
| F | F | Gm | Am | B♭ | C | Dm | E° |
| B♭ | B♭ | Cm | Dm | E♭ | F | Gm | A° |

## Key-independent

A progression written in numerals is **key-independent**: I–IV–V is C F G in C, G C D in G and E A B in E. This is the basis of transposing chords (lesson 5.7). Writing a progression out in numerals is **Roman numeral analysis**.

## Other systems

- All uppercase with “m” for minor (IIm, IIIm, VIm), used in some books, including Goodman.
- The Nashville number system with Arabic numbers (Module 15).

This site uses the uppercase/lowercase style everywhere, as in the Key Chords tool. A chord outside the key is written with an accidental before the numeral: ♭VII in C is B♭ (Module 14).

## Try it

Write I–vi–IV–V in G, D and F, then play its roots.

## New terms

- Roman numeral
- Roman numeral analysis

Page: https://bazzlow.com/en/harmony-in-a-key/roman-numerals/