major scale: seven notes on whole and half steps

One run of steps, counted in semitones

Every major key uses this one run of steps, so the run is what makes a scale major. In steps it is whole, whole, half, whole, whole, whole, half; in semitones that is 2, 2, 1, 2, 2, 2, 1. A whole step is two semitones and a half step is one, so the seven steps add to 12 — one octave, in every key, from any starting note.

Five whole steps and two half steps: 5 × 2 + 2 × 1 = 10 + 2 = 12 semitones. Twelve semitones is the distance from a note to its octave, so a pattern that adds to 12 lands on the same letter an octave higher; a pattern that added to anything else could not be a seven-note scale inside one octave.

The starting note also decides how many sharps or flats the signature carries. The two keys with one accidental each are on the one sharp page (G major, F♯) and the one flat page (F major, B♭); the count for every signature is on the key signature chart.

C major from C4 to C5, one line of arithmetic each

Equal temperament with A4 = 440 Hz puts a pitch at 440 × 2^{((midi − 69) ÷ 12)} Hz, where midi is the note’s number on the MIDI scale: C4 is 60, A4 is 69, C5 is 72. The eight notes of C major from C4 to C5, each with its own line:

The eight numbers are not eight separate facts: C5 is exactly twice C4, so the last row is the first row doubled before rounding. Every other major key takes the same twelve pitches of the octave and starts them somewhere else, so this arithmetic covers all of them.

The twelve major scales, with their sharps or flats

Twelve keys, one per semitone, each spelled with the seven letters it needs. The sharps and flats are the ones on the key signature chart, so the count in the second column and the accidentals in the third have to agree. The last column is the Camelot code for the same key, taken from this site’s Camelot scale page.

Twelve rows, not fifteen: F♯ major and G♭ major are the same seven pitches, this page keeps the sharp spelling, and that leaves C♯ major with seven sharps and C♭ major with seven flats off the table. Both of those signatures are rows of the key signature chart like any other, and B major is spelled out again on the five sharps page.

Every row above is a major key. The minor scale keeps the same seven letters but lowers the third, sixth and seventh, and its three forms are spelled out on the minor scale page.

When the key finder says a key, read the row

The key finder answers with a key name, a Camelot code and a confidence. When it says C major, the seven notes are the C major row above — C, D, E, F, G, A, B — and the code is 8B; when it says E♭ major the row is E♭, F, G, A♭, B♭, C, D and the code is 5B. The detector names a tonal centre, this table turns that name into the notes you can play, and the Camelot code is what a mixing tool reads.

The confidence matters as much as the name. 55% means the finder still sees another key fitting the same audio, and the honest reading is to check both rows before trusting either — a reading in the fifties names a shortlist, not one key.

A recorded example you can check

The key has two separate sources. The engraved score prints no sharps and no flats at the start of either staff, and heads the piece “Praeludium 1 / BWV 846”. The Wikipedia article The Well-Tempered Clavier, read on 23 October 2026, lists “No. 1: Prelude and Fugue in C major, BWV 846” in its Book 1 table. A blank signature read off a staff and a catalogue entry in an encyclopaedia are different documents, and they agree.

On 23 October 2026 at 05:30 EDT this site’s key finder read this 24-second clip as C major, Camelot 8B, at 55% confidence, and labelled the reading low. It listed F major (Camelot 7B, 28%) and C minor (Camelot 5A, 6%) next, and its on-screen note says F major also fits and that the melody or chords should be checked before mixing. That percentage is the finder’s estimate for this file, not a measured accuracy rate. The printed key and the reading agree; the 55% is the finder saying F major, the key on the fourth degree, also fits the same arpeggios.

A second count of the same file, made here from the audio alone rather than from the finder, puts 98.0% of the energy in the seven pitch classes of C major and 2.0% in the other five. The strongest single class is D at 19.9%, ahead of C at 13.6%, which is what counting energy does to an arpeggiated prelude: it can confirm the seven notes, it cannot say which of them is home.

Major scale: quick answers

What this page leaves open

• The frequencies are equal temperament at A4 = 440 Hz. Another tuning puts the same letter names at different numbers.
• Twelve rows, one per semitone. The enharmonic spellings C♯ major, C♭ major and G♭ major are not tabulated here.
• 55% is the finder’s estimate for this 24-second file, not an accuracy rate, and another pianist’s prelude will read differently.
• A scale is seven names. A piece in C major still writes notes outside them.
• Modes, chords and the relative minor are other pages.