B Note Frequency — B0 to B7
B is the last note before the octave repeats. B major and B minor are common guitar and rock keys, and the open second string on a guitar is B3.
Every B on an 88-key piano
Frequencies use equal temperament with A4 = 440 Hz. Range shown: B0 to B7 — 8 of the 88 keys.
| Note | MIDI number | Frequency (Hz) |
|---|---|---|
| B0 | 23 | 30.87 |
| B1 | 35 | 61.74 |
| B2 | 47 | 123.47 |
| B3 | 59 | 246.94 |
| B4 | 71 | 493.88 |
| B5 | 83 | 987.77 |
| B6 | 95 | 1975.53 |
| B7 | 107 | 3951.07 |
How the frequency of B 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 B4 that is
m = 71, giving 493.88 Hz.
B 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 B4 at 493.88 Hz has a neighbour 466.16 Hz a semitone below and 523.25 Hz a semitone above, and B5 at 987.77 Hz an octave above.
Frequently asked questions
- What is the frequency of B4?
- B4 is 493.88 Hz in equal temperament with A4 = 440 Hz. It is MIDI note 71.
- How many B notes are on an 88-key piano?
- An 88-key piano runs from A0 to C8 and contains 8 B notes, from B0 (30.87 Hz) to B7 (3951.07 Hz).
- What MIDI number is B4?
- B4 is MIDI note 71. 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