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What does this calculator estimate?
440 Hz maps to MIDI note 69, which is A4, exactly on pitch. 466 Hz lands near MIDI 70 (A#4), within a few cents of the equal-tempered note. MIDI = round(12 x log2(freq / 440)) + 69.
- MIDI note = round(12 x log2(freq / 440)) + 69.
- 440 Hz is A4, the standard tuning reference.
- Cents measure detuning: 100 cents = one semitone.
How frequencies map to notes
Musical notes are logarithmically spaced: each semitone multiplies the frequency by the twelfth root of 2 (≈1.0595). A4 is the reference at 440 Hz, and every other note is computed from it. The tool rounds to the nearest note and reports the detuning in cents.
Limitations to watch for
The standard is A440 equal temperament — baroque tunings (A415) and other temperaments shift the mapping. The result is the closest note; a large cents value means the input is between notes. Very low or high frequencies map to extreme octaves.
How to use it in practice
Use it to tune instruments (a tuner reading 442 Hz means you're 8 cents sharp of A4), identify hum frequencies in recordings, or map synth oscillators to notes. Check the cents value to see how far off the note you are.
['Enter a frequency in Hz.', 'The tool computes the closest note name, MIDI number, and cents deviation.', 'Use the cents to judge how far off-pitch the input is.']
How frequency maps to notes
Musical notes are frequencies: A4 = 440 Hz, and each semitone multiplies by 2^(1/12). The calculator converts a frequency to the nearest note and cents offset, and a note to its exact frequency.
The 440 Hz standard
A4 = 440 Hz is the international tuning standard. Some ensembles tune to 442 or 443 Hz for a brighter sound. The calculator lets you set the reference so tuning comparisons match your context.
Cents measure the gap
One hundred cents equals one semitone. A frequency 10 Hz above A4 (450 Hz) is about 39 cents sharp — clearly audible. The cents offset tells a musician whether to tune up or down and by how much.
A worked example
440 Hz is A4 exactly. 523.25 Hz is C5 — the 'middle C' region (in scientific pitch, C4 = 261.63 Hz). 880 Hz is A5, an octave above A4. The calculator returns note names and octaves for any frequency.
Practical uses
Tuning instruments, checking a synth patch, identifying a hum's pitch (60 Hz mains hum is close to B1), and setting a reference for ear training. The calculator is the bridge between the waveform and the note name.
How this calculator works
Formula
MIDI note = round(12 × log₂(frequency ÷ 440)) + 69 (A4 = 440 Hz = MIDI 69). Note name from MIDI % 12 and octave from MIDI ÷ 12 − 1. Detuning in cents = 1200 × log₂(f ÷ 440) − 1200 × (MIDI − 69).
Worked example
440 Hz → A4 (MIDI 69). 261.63 Hz → C4 (MIDI 60) — middle C.
Assumptions to verify
- A440 equal temperament tuning.
- The closest note is reported (with cents deviation).
- MIDI note numbering (C4 = 60).
Frequently asked questions
How do I convert frequency to a note?
The tool computes MIDI = round(12 × log₂(f/440)) + 69, then maps MIDI to a note name. 440 Hz → A4, 261.63 Hz → C4.
What is A4 = 440 Hz?
The standard tuning reference: the A above middle C is 440 Hz, MIDI note 69.
What is a cent?
One hundredth of a semitone. A tuner showing +8 cents means you're 8/100 of a semitone sharp.
How are notes spaced in frequency?
Each semitone is a factor of 2^(1/12) ≈ 1.0595 — 12 semitones double the frequency (one octave).
Why does my tuner disagree with this?
Different temperaments and reference pitches exist (A415 baroque, A442 orchestral). This tool uses standard A440 equal temperament.
What if the cents value is large?
The input is significantly between two notes — you may be hearing a different note entirely or the frequency is out of tune.
What is MIDI note numbering?
The standard that maps notes to numbers: C4 (middle C) = 60, A4 = 69, C5 = 72. It's used in synthesizers and digital audio.
What is 440 Hz?
A4, the standard tuning reference.
What note is 60 Hz?
Close to B1 — mains hum is often heard as a low B.
Cite this tool
BoringToolsKit. “Frequency to Note Converter.” boringtoolskit.com/frequency-to-note-calculator/ (reviewed 2026-08-25). Free to reference in articles, syllabi, and answer posts with a link.
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