What this calculator does
Chord progressions are described using Roman numerals that represent scale degrees, like I-IV-V-I. This tool converts a chosen progression into the actual chord names for any key.
How the calculation works
Each note of a major or natural minor scale supports a chord with a specific quality (major, minor, or diminished) determined purely by its position in the scale — for example, in a major key the I, IV, and V chords are major while ii, iii, and vi are minor and vii is diminished. The calculator maps your chosen progression’s scale degrees to notes in your chosen key and quality using this diatonic pattern.
This reflects standard tonal harmony theory used across pop, rock, jazz, and classical music, though real songs frequently borrow chords from outside the strict diatonic set.