What frequency is A4?

A4 is 440 Hz. It is the international tuning reference (ISO 16) and MIDI note 69. You can read more on the A4 = 440 Hz page.

What is the frequency range of an 88-key piano?

A standard 88-key piano runs from A0 at 27.50 Hz to C8 at 4186.01 Hz.

What is middle C in Hz?

Middle C (C4, MIDI 60) is 261.63 Hz. Note that some manufacturers, Yamaha among them, label this note C3 — the sound is identical, only the octave numbering differs.

How do you calculate a note frequency from a MIDI number?

Use f = 440 × 2^((m − 69) / 12), where m is the MIDI note number. MIDI 69 is A4 = 440 Hz, MIDI 60 is middle C, and each increase of 12 doubles the frequency.

Do these frequencies change between instruments?

The nominal frequencies do not, but real instruments vary. Pianos are stretched-tuned slightly, orchestras sometimes tune to 442 or 443 Hz rather than 440, and wind players bend pitch by design. The table gives the theoretical equal-temperament values.

Note Frequency Chart — All 88 Piano Keys

Every note on a standard 88-key piano, from A0 to C8, with its exact frequency in hertz and its MIDI note number. Values use twelve-tone equal temperament with A4 = 440 Hz, the international tuning standard (ISO 16).

Full range: A0 – C8

Click any note to see that pitch class across every octave.

Note	MIDI number	Frequency (Hz)
A0	21	27.50
A♯0	22	29.14
B0	23	30.87
C1	24	32.70
C♯1	25	34.65
D1	26	36.71
D♯1	27	38.89
E1	28	41.20
F1	29	43.65
F♯1	30	46.25
G1	31	49.00
G♯1	32	51.91
A1	33	55.00
A♯1	34	58.27
B1	35	61.74
C2	36	65.41
C♯2	37	69.30
D2	38	73.42
D♯2	39	77.78
E2	40	82.41
F2	41	87.31
F♯2	42	92.50
G2	43	98.00
G♯2	44	103.83
A2	45	110.00
A♯2	46	116.54
B2	47	123.47
C3	48	130.81
C♯3	49	138.59
D3	50	146.83
D♯3	51	155.56
E3	52	164.81
F3	53	174.61
F♯3	54	185.00
G3	55	196.00
G♯3	56	207.65
A3	57	220.00
A♯3	58	233.08
B3	59	246.94
C4	60	261.63
C♯4	61	277.18
D4	62	293.66
D♯4	63	311.13
E4	64	329.63
F4	65	349.23
F♯4	66	369.99
G4	67	392.00
G♯4	68	415.30
A4	69	440.00
A♯4	70	466.16
B4	71	493.88
C5	72	523.25
C♯5	73	554.37
D5	74	587.33
D♯5	75	622.25
E5	76	659.26
F5	77	698.46
F♯5	78	739.99
G5	79	783.99
G♯5	80	830.61
A5	81	880.00
A♯5	82	932.33
B5	83	987.77
C6	84	1046.50
C♯6	85	1108.73
D6	86	1174.66
D♯6	87	1244.51
E6	88	1318.51
F6	89	1396.91
F♯6	90	1479.98
G6	91	1567.98
G♯6	92	1661.22
A6	93	1760.00
A♯6	94	1864.66
B6	95	1975.53
C7	96	2093.00
C♯7	97	2217.46
D7	98	2349.32
D♯7	99	2489.02
E7	100	2637.02
F7	101	2793.83
F♯7	102	2959.96
G7	103	3135.96
G♯7	104	3322.44
A7	105	3520.00
A♯7	106	3729.31
B7	107	3951.07
C8	108	4186.01

The formula behind these numbers

Equal temperament divides the octave into twelve equal semitones, so one semitone is a ratio of the twelfth root of two. With A4 (MIDI 69) fixed at 440 Hz, the frequency of any MIDI note m is:

f = 440 × 2^{(m − 69) / 12}

Two useful consequences: moving up one octave doubles the frequency, and moving up one semitone multiplies it by about 1.0595 (roughly 5.95%).

Landmark notes

A0 — 27.50 Hz, the lowest note on a standard piano.
C4 (middle C) — 261.63 Hz, MIDI 60. More on middle C.
A4 — 440.00 Hz, MIDI 69, the tuning reference. More on A4 = 440 Hz.
C8 — 4186.01 Hz, the highest note on a standard piano.

Frequently asked questions

What frequency is A4?: A4 is 440 Hz. It is the international tuning reference (ISO 16) and MIDI note 69. You can read more on the A4 = 440 Hz page.
What is the frequency range of an 88-key piano?: A standard 88-key piano runs from A0 at 27.50 Hz to C8 at 4186.01 Hz.
What is middle C in Hz?: Middle C (C4, MIDI 60) is 261.63 Hz. Note that some manufacturers, Yamaha among them, label this note C3 — the sound is identical, only the octave numbering differs.
How do you calculate a note frequency from a MIDI number?: Use f = 440 × 2^((m − 69) / 12), where m is the MIDI note number. MIDI 69 is A4 = 440 Hz, MIDI 60 is middle C, and each increase of 12 doubles the frequency.
Do these frequencies change between instruments?: The nominal frequencies do not, but real instruments vary. Pianos are stretched-tuned slightly, orchestras sometimes tune to 442 or 443 Hz rather than 440, and wind players bend pitch by design. The table gives the theoretical equal-temperament values.

Last updated: 2026-09-01