C Note Frequency — C1 to C8
C is the simplest key centre on the keyboard: the C major scale uses only white keys, which is why beginners meet it first and why so much teaching material is written in C. C4 (middle C) is the anchor point most players learn to read from.
Every C on an 88-key piano
Frequencies use equal temperament with A4 = 440 Hz. Range shown: C1 to C8 — 8 of the 88 keys.
| Note | MIDI number | Frequency (Hz) |
|---|---|---|
| C1 | 24 | 32.70 |
| C2 | 36 | 65.41 |
| C3 | 48 | 130.81 |
| C4 | 60 | 261.63 |
| C5 | 72 | 523.25 |
| C6 | 84 | 1046.50 |
| C7 | 96 | 2093.00 |
| C8 | 108 | 4186.01 |
How the frequency of C is calculated
Modern instruments use twelve-tone equal temperament, where an octave is split into twelve equal semitones. With A4 fixed at 440 Hz, any note’s frequency is:
f = 440 × 2(m − 69) / 12
where m is the MIDI note number. For C4 that is
m = 60, giving 261.63 Hz.
C and its neighbours
Each semitone changes the frequency by a ratio of 21/12 ≈ 1.0595 — about 5.95%. Going up one octave doubles it. So C4 at 261.63 Hz has a neighbour 246.94 Hz a semitone below and 277.18 Hz a semitone above, and C5 at 523.25 Hz an octave above.
Frequently asked questions
- What is the frequency of C4?
- C4 is 261.63 Hz in equal temperament with A4 = 440 Hz. It is MIDI note 60.
- How many C notes are on an 88-key piano?
- An 88-key piano runs from A0 to C8 and contains 8 C notes, from C1 (32.70 Hz) to C8 (4186.01 Hz).
- What MIDI number is C4?
- C4 is MIDI note 60. MIDI note numbers run from 0 (C−1) to 127 (G9), with middle C (C4) at 60 and A4 at 69.
- Why does the frequency double every octave?
- An octave is a 2:1 frequency ratio. In twelve-tone equal temperament the octave is divided into twelve equal steps, so each semitone multiplies the frequency by the twelfth root of two (about 1.0595). Twelve of those steps multiply out to exactly 2.
Last updated: 2026-09-01