Frequency to Note Converter
Convert any frequency in Hz to the nearest musical note with cents offset, or find the exact frequency of any note. Supports A4 = 432, 440, or 442 Hz — free, browser-based, no download.
→ Frequency to Note
← Note to Frequency
How to Use the Converter
- Hz → Note: Enter a frequency in Hz (e.g., 440) to see the nearest note, octave, and cents offset.
- Note → Hz: Click a note name and octave to see its exact frequency.
- Change the A4 reference (432 / 440 / 442 Hz) if your instrument uses non-standard tuning.
- Toggle flats (♭) if you prefer Db over C#, Bb over A#, etc.
- Use the quick buttons for common reference frequencies and notes.
Common Hz to Note Reference
440 Hz is A4 (concert pitch), 261.63 Hz is C4 (middle C), and 329.63 Hz is E4 (guitar high E). Use this quick lookup to identify the note for any common frequency without doing the math.
| Frequency | Note | Context |
|---|---|---|
| 27.50 Hz | A0 | Lowest note on an 88-key piano |
| 82.41 Hz | E2 | Low E string — guitar |
| 110.00 Hz | A2 | A string — guitar |
| 196.00 Hz | G3 | G string — guitar / violin |
| 220.00 Hz | A3 | A below middle C |
| 246.94 Hz | B3 | B below middle C |
| 261.63 Hz | C4 | Middle C |
| 293.66 Hz | D4 | D above middle C |
| 329.63 Hz | E4 | High E string — guitar |
| 440.00 Hz | A4 | Concert pitch (ISO 16) |
| 523.25 Hz | C5 | C above middle C |
| 880.00 Hz | A5 | One octave above A4 |
The Conversion Formula
The relationship between frequency and musical notes is based on the equal-tempered scale, where each octave is divided into 12 equal semitones. Given a reference frequency for A4 (standard: 440 Hz), any note's frequency can be calculated:
f = A4 × 2(n − 69) / 12
where n is the MIDI note number (A4 = 69) and A4 = 440 Hz
To go the other direction — frequency to note — invert the formula:
n = 69 + 12 × log2(f / A4)
The integer part of n gives the nearest MIDI note (which maps to a note name and octave), and the fractional part multiplied by 100 gives the cents offset — how far the frequency is from the exact note.
Note Frequency Reference Table
Standard equal-tempered frequencies for common musical notes (A4 = 440 Hz). Use this as a quick lookup for instrument tuning and audio calibration.
| Note | Frequency | MIDI | Common Use |
|---|---|---|---|
| C0 | 16.35 Hz | 0 | Lowest audible piano-style note |
| A0 | 27.50 Hz | 21 | Lowest key on a standard 88-key piano |
| E1 | 41.20 Hz | 28 | Lowest note on a 4-string bass (B0 on 5-string) |
| E2 | 82.41 Hz | 40 | Low E string — guitar (standard tuning) |
| A2 | 110.00 Hz | 45 | A string — guitar |
| C3 | 130.81 Hz | 48 | Low C — cello C-string |
| G3 | 196.00 Hz | 55 | G string — guitar / violin G-string |
| C4 | 261.63 Hz | 60 | Middle C — piano center |
| A4 | 440.00 Hz | 69 | Concert pitch reference (ISO 16) |
| C5 | 523.25 Hz | 72 | C one octave above middle C |
| A5 | 880.00 Hz | 81 | A one octave above A4 |
| C8 | 4186.01 Hz | 108 | Highest key on a standard piano |
What Is a Frequency-to-Note Converter Used For?
Instrument tuning
If you know the target frequency of a string or key, convert it to a note name to verify your tuner is showing the right pitch — especially useful for alternate tunings.
Audio engineering
Identify which musical note corresponds to a resonant frequency, hum, or whine in a recording. Common power-line hum at 50/60 Hz is near G1 (49 Hz) / B1 (62 Hz).
Acoustics education
Demonstrate the logarithmic relationship between frequency and pitch. Students can explore why each octave doubles the frequency (e.g., A4 = 440, A5 = 880).
Hearing tests
Convert audiometric test frequencies (250, 500, 1000, 2000, 4000, 8000 Hz) to musical notes to understand what pitches audiologists are checking.
Microtonal music
Composers working in non-standard tunings (just intonation, 31-EDO, etc.) can use the cents offset to quantify how far a frequency deviates from equal temperament.
Synthesizer programming
When dialing in an oscillator frequency on a hardware synth or modular system, convert the raw Hz value to a note name to place it in a musical context.
Frequently Asked Questions
Use the formula MIDI = 69 + 12 × log2(frequency / 440). The integer part maps to a note name and octave; the fractional part gives the cents offset. For example, 440 Hz → A4 (0 cents), 261.63 Hz → C4 (0 cents).
A4 = 440 Hz in standard concert pitch (ISO 16:1975). Some orchestras use 442 Hz for a brighter sound. This converter supports 432, 440, 442 Hz, or any custom A4 value between 400–460 Hz.
A cent is 1/100 of a semitone. There are 100 cents between adjacent notes (e.g., C4 and C#4). The cents offset shows how far a frequency is from the nearest standard note. +5 cents = 5 cents sharp; −3 cents = 3 cents flat. Most people can't hear differences smaller than 5–10 cents.
frequency = A4 × 2^((MIDI − 69) / 12). With A4 = 440 Hz, C5 (MIDI 72) = 440 × 2^(3/12) ≈ 523.25 Hz. This converter calculates it instantly — just pick a note and octave.
Most real-world frequencies don't land exactly on a standard equal-tempered note. 445 Hz is about 19 cents sharp of A4 (440 Hz). The cents offset tells you the tuning deviation — useful for instrument tuning and acoustic analysis.
440 Hz is the international standard (ISO 16) since 1955. 442 Hz is used by some European orchestras for brightness. 432 Hz is a popular alternative with no proven audio advantage but some prefer its warmer tone. All three are supported here.