A semitone is the smallest step in Western music: the distance from one piano key to the very next key, black or white. It is also called a half step. Twelve semitones make an octave, and each one raises the frequency by 5.95 %. Count semitones between any two notes with the semitone calculator.
What is a semitone in music?
In the equal temperament used by pianos, guitars and almost all modern music, the octave is split into 12 equal semitones. C to C♯, E to F and B to C are each one semitone. The word comes from Latin semi (half) and “tone” (a whole step); American books say “half step”, British books “semitone”. The Wikipedia entry on the semitone covers the history.
What is a semitone on the piano?
On a keyboard, a semitone is any two neighbouring keys. Most pairs are a white key and a black key (C–C♯), but two pairs of white keys have no black key between them: E–F and B–C. So yes, B to C is a semitone. On a guitar, one semitone is one fret.
Semitone vs tone: half step vs whole step
| Name | Also called | Semitones | Cents | Example | Frequency ratio |
|---|---|---|---|---|---|
| Semitone | Half step, minor second | 1 | 100 | E → F, C → C♯ | 1.0595 |
| Tone | Whole step, major second | 2 | 200 | C → D, E → F♯ | 1.1225 |
| Quarter tone | Half a semitone | ½ | 50 | Arabic maqam (approx.) | 1.0293 |
| Octave | 12 semitones | 12 | 1,200 | C4 → C5 | 2.0000 |
So a whole step is 2 semitones, and a half step is 1. The major scale is built from the pattern tone–tone–semitone–tone–tone–tone–semitone (W–W–H–W–W–W–H); C major uses only white keys because its two semitones fall on E–F and B–C.
How many semitones are in an octave?
Twelve. Starting on C, the 12 semitones are C, C♯, D, D♯, E, F, F♯, G, G♯, A, A♯, B, and the thirteenth note is C again, one octave up. Playing all 12 in a row gives the chromatic scale, the “semitone scale”. Every other interval is a number of semitones:
| Semitones | Interval | From C |
|---|---|---|
| 0 | Unison | C–C |
| 1 | Minor second (half step) | C–D♭ |
| 2 | Major second (whole step) | C–D |
| 3 | Minor third | C–E♭ |
| 4 | Major third | C–E |
| 5 | Perfect fourth | C–F |
| 6 | Tritone | C–F♯ |
| 7 | Perfect fifth | C–G |
| 8 | Minor sixth | C–A♭ |
| 9 | Major sixth | C–A |
| 10 | Minor seventh | C–B♭ |
| 11 | Major seventh | C–B |
| 12 | Octave | C–C |
Semitones, cents and Hz: reference chart
A semitone is a fixed ratio, not a fixed number of hertz. Each step multiplies the frequency by 1.05946, so higher notes have wider semitones in Hz. The chart starts from A4 = 440 Hz, the standard tuning pitch; the last column is the speed change a record player would need for the same pitch shift.
| Semitones | Ratio | Cents | A4 440 Hz becomes | Varispeed change |
|---|---|---|---|---|
| −12 | 0.5000 | −1200 | 220.00 Hz (A3) | −50.00 % |
| −7 | 0.6674 | −700 | 293.66 Hz (D4) | −33.26 % |
| −5 | 0.7492 | −500 | 329.63 Hz (E4) | −25.08 % |
| −3 | 0.8409 | −300 | 369.99 Hz (F♯4) | −15.91 % |
| −2 | 0.8909 | −200 | 392.00 Hz (G4) | −10.91 % |
| −1 | 0.9439 | −100 | 415.30 Hz (G♯4) | −5.61 % |
| +1 | 1.0595 | +100 | 466.16 Hz (A♯4) | +5.95 % |
| +2 | 1.1225 | +200 | 493.88 Hz (B4) | +12.25 % |
| +3 | 1.1892 | +300 | 523.25 Hz (C5) | +18.92 % |
| +5 | 1.3348 | +500 | 587.33 Hz (D5) | +33.48 % |
| +7 | 1.4983 | +700 | 659.26 Hz (E5) | +49.83 % |
| +12 | 2.0000 | +1200 | 880.00 Hz (A5) | +100.00 % |
| Note | Frequency | One semitone up | Width of that semitone |
|---|---|---|---|
| A2 | 110.00 Hz | 116.54 Hz | 6.54 Hz |
| A3 | 220.00 Hz | 233.08 Hz | 13.08 Hz |
| A4 | 440.00 Hz | 466.16 Hz | 26.16 Hz |
| A5 | 880.00 Hz | 932.33 Hz | 52.33 Hz |
| A6 | 1760.00 Hz | 1864.66 Hz | 104.66 Hz |
That is why pitch tools work in semitones and pitch is heard as a ratio: a 26 Hz step is a semitone at A4 but only a quarter of one at A6. Our semitone calculator, linked above, matched in QA the formulas for all 11,664 note pairs, and how our tools are tested lists the method.
Semitones and cents: can a step be smaller?
Yes. Each semitone is divided into 100 cents, so a cent is 1/1,200 of an octave. Tuners show cents, and most listeners notice differences of about 5 to 10 cents between two notes played one after the other. Half a semitone (50 cents) is a quarter tone. Across 11 QA exports from −24 to +24 semitones, our pitch shifter stayed within 0.099 cents of the target.
Chromatic vs diatonic semitone
C to C♯ keeps the letter name and is called a chromatic semitone; C to D♭ changes the letter and is a diatonic semitone (a minor second). In equal temperament both are exactly 100 cents. In just intonation they differ: the diatonic semitone 16:15 is 111.7 cents and the chromatic 25:24 only 70.7 cents; the Pythagorean limma (256:243) is 90.2 cents.
How semitones are used to change pitch and key
Moving a whole song up or down by a number of semitones is transposition. One semitone up turns C major into D♭ major; two semitones turn it into D major. A key change up one semitone near the end of a pop song is the classic semitone modulation. To hear any song in a new key, use the online key changer, which names the new key at each step, or the music key chart to see the notes of every key.
- How many semitones between two specific keys: how many semitones to change key (full 12 × 12 table).
- Key vs pitch, and transpose vs pitch shift: key change vs pitch change.
- Singers with a song out of range: song too high, song too low and male to female key change.
- Semitones change pitch, not tempo: pitch vs tempo and change pitch without changing speed.
Frequently asked questions
How many semitones are in a whole step?
Two. A whole step (tone) is 2 semitones or 200 cents, for example C to D.
How many semitones is a half step?
One. “Half step” is the American name for a semitone.
Is B to C a semitone?
Yes. B–C and E–F are the two natural semitones: there is no black key between them.
What is half a semitone?
A quarter tone: 50 cents, a frequency ratio of about 1.0293. Western notation rarely uses it; you can set it as −0.5 or +0.5 semitones in a pitch tool.
How many cents are in a semitone?
100 cents in equal temperament, so an octave has 1,200 cents.
What does 2 semitones lower mean?
Every note moves down two piano keys (a whole step): a song in E becomes D, and A4 = 440 Hz becomes G4 = 392 Hz. Try it on the online pitch changer, see the voice type test for singers, or browse all pitch and key guides.