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Hz to Note Converter

Enter any frequency in Hertz to find the nearest musical note, cent deviation from equal temperament, MIDI number, and octave. Visual single-octave piano, side-by-side audio comparison, and adjustable A4 reference tuning (380–480 Hz).

Input

Frequency (Hz)

Hz

A4 Reference Tuning

Hz

380440480

A4 = 440.0 Hz (current reference)

Common Frequencies

Nearest Note

A4

Cents Deviation

+0.00

¢ from equal-tempered

−50 ¢ (flat)0+50 ¢ (sharp)

+0.00 ¢

Perfect (within 1 ¢)

Midrange

Single-octave keyboard — matched key highlighted

MIDI Number

—

Exact Note Freq

—

Period (T = 1/f)

—

Wavelength in Air

—

Algorithm

MIDI = round(12 × log₂(f / A4) + 69)

cents = 1200 × log₂(f / f_nearest_note)

—

Cents Deviation — Musical Perception Guide

Cents off	Frequency ratio	Musical perception	Examples
0 – 1 ¢	1.0000 – 1.00058	Perfect — indistinguishable	Studio reference; lab instruments
1 – 5 ¢	1.0006 – 1.0029	Imperceptible to untrained ears	Well-tuned instruments
5 – 15 ¢	1.0029 – 1.0087	Audible to trained musicians	Slightly out of tune piano
15 – 30 ¢	1.0087 – 1.0175	Audible to most listeners	Cheap consumer tuning
30 – 50 ¢	1.0175 – 1.0293	Clearly out of tune	Approaches a quarter-tone
50 – 100 ¢	1.0293 – 1.0595	Almost a different note	Approaching the next semitone
100 ¢ (exactly)	1.0595 (12√2)	One whole semitone away	Definitely a different note

About Cents, Notes & Tuning

Every musical note in 12-tone equal temperament has an exact frequency. When you measure a real-world frequency (from a tuning fork, an instrument, a recording, or a sound generator), it rarely lands precisely on a note — it's usually slightly sharp (above) or flat (below). The cents value tells you how far off you are.

How the cent works

A cent is 1/100th of an equal-tempered semitone. There are 1,200 cents in an octave. The formula is cents = 1200 × log₂(f / f_target). A positive value means the input frequency is sharp (higher than the target note); a negative value means flat. Trained musicians can typically detect deviations of 5–10 cents; untrained listeners notice 15–25 cents and above.

Why the A4 reference matters

Every note's frequency is calculated relative to A4. Change A4 from 440 to 432 Hz and every note shifts proportionally — Middle C goes from 261.63 to 256.87 Hz. If you measure a 261.63 Hz tone with A4 = 432 reference, you'll see it's now +32 cents sharp relative to that tuning system. This tool lets you switch the reference freely to test alternative tunings.

What can shift a note's measured frequency?

Microphone latency and aliasing, room reverb and resonance, the natural inharmonicity of strings (especially piano bass strings), vibrato in singing, temperature-driven tuning drift, and intentional pitch-bending in performance. A "perfect" reading in software doesn't always mean a perfect performance — context matters.

Frequently Asked Questions

How do I convert Hz to a musical note?

Use the formula MIDI = round(12 × log₂(f / A4) + 69), then look up the note name from the MIDI number. For example, 442 Hz at A4 = 440: MIDI = round(12 × log₂(442/440) + 69) = round(69.0788) = 69, which is A4 — but 7.88 cents sharp.

What does "cents" mean in music?

A cent is 1/100th of a semitone, so 1,200 cents = 1 octave. It's a logarithmic unit, meaning the same number of cents represents the same musical interval no matter what the base frequency. 10 cents between 100 Hz and 100.578 Hz sounds like the same "amount of sharpness" as 10 cents between 1000 Hz and 1005.78 Hz.

How accurate do I need my tuning to be?

For concert performance, ±5 cents is usually considered well-tuned. Studio recordings often aim for ±3 cents on important pitches. Beyond ±15 cents, most listeners can hear the wobble. Choirs naturally fluctuate ±10 cents during phrases — perfectionism beyond a certain point is musically unnatural.

Why isn't 1,000 Hz a real note?

1,000 Hz is the standard audio test tone but it falls between B5 (987.77 Hz) and C6 (1046.50 Hz) — roughly 21 cents sharp of B5. Audio engineers chose 1 kHz for testing because it's mid-range, easy to hear, easy to generate accurately, and not at any musically-meaningful pitch (avoids being confused with intentional musical content).

Why does mains hum show as a specific note?

60 Hz (US power) sits 49 cents below B1 (61.74 Hz), so it sounds roughly like a flat-B in the deep bass. 50 Hz (Europe/Asia) is closer to a G1 (49 Hz), just slightly sharp. This is why electric hum can be musically intrusive — it lands in or near specific bass notes.

What's the difference between Play Input and Play Nearest Note?

Play Input generates your exact frequency (e.g., 442 Hz). Play Nearest Note plays the equal-tempered target (e.g., A4 = 440 Hz). Switch between them quickly to hear how "wrong" the cents deviation actually sounds — for small values you may not hear a difference, for larger ones the gap is obvious.

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