Frequency to Musical Note Calculator — Convert Hz to Notes and Back
Convert any frequency in Hz to its musical note name, octave, and cents deviation. Essential for tuning, sound design, and understanding the physics of music.
A 440 Hz sine wave and the note A4 are the same thing — but most musicians think in note names and most synths display in Hz. The conversion calculator bridges that gap, and it's more useful than you might expect across tuning, synthesis, and acoustic analysis.
Try it at CalcHub — enter any Hz value, get the note name, octave, and how many cents sharp or flat it is.
The Math Behind the Conversion
Western music uses equal temperament tuning, where each octave divides into 12 equally-spaced semitones. Starting from A4 = 440 Hz, every semitone up multiplies the frequency by the 12th root of 2 (≈ 1.05946). Every octave up doubles the frequency.
The formula for finding note number from frequency:
n = 12 × log₂(f ÷ 440) + 69
Where n is the MIDI note number. From n you can derive the note name and octave.
Frequency Reference Table
| Note | Octave | Frequency |
|---|---|---|
| C | 2 | 65.41 Hz |
| A | 3 | 220 Hz |
| Middle C (C4) | 4 | 261.63 Hz |
| A (concert pitch) | 4 | 440 Hz |
| A | 5 | 880 Hz |
| C | 6 | 1046.50 Hz |
| A | 6 | 1760 Hz |
Cents: When Notes Are In Between
One cent = 1/100th of a semitone. When a frequency falls between two notes, the calculator shows which note it's nearest to and how many cents sharp or flat. Useful for:
- Instrument tuning: A string vibrating at 442 Hz is 7.8 cents sharp of A440
- Microtonality: Some music intentionally uses frequencies between standard notes
- Acoustic analysis: Singing or playing slightly off-pitch shows up as cents deviation
Applications Beyond Basic Tuning
Synthesizer design: Creating a chord in a synth sometimes means entering exact Hz values. Knowing that a perfect fifth above A4 (440 Hz) is E5 (659.25 Hz) helps you program intervals precisely. Room acoustics: Room resonance frequencies can be calculated and compared to musical notes. A room with a resonance at 80 Hz is boosting the note E2 — useful for acoustic treatment decisions. Sound design: Matching a low rumble, explosion, or bass hit to a specific note makes it sit better in a musical context. A kick drum tuned to the root note of the song just sounds tighter. Alternative tuning systems: Some musicians tune to A=432 Hz, A=444 Hz, or other reference pitches. The calculator handles any reference frequency.What is A440 and why is it the standard?
A440 (A4 = 440 Hz) became the international standard tuning reference in 1939 and was confirmed by ISO in 1975. Before standardization, concert pitch varied wildly — orchestras in different cities often tuned to different references, making it impossible to collaborate without transposing. A440 isn't physically special; it's simply agreed-upon.
Why do some people prefer A432?
The A432 tuning movement claims it sounds "more natural" or harmonically richer. The scientific basis for this claim is weak — it's mostly aesthetic preference. Many great recordings were made at A440, A442, and other references. The difference is so small (less than 8 cents) that most listeners can't tell without a direct comparison.
How does this relate to MIDI note numbers?
MIDI uses numbers 0–127 for notes. Middle C is MIDI note 60. A4 (440 Hz) is MIDI note 69. Each semitone up increments by 1. The calculator can show you the MIDI number for any frequency, which is useful for programming synths and controllers.
Related Calculators
- Key Transposer Calculator — transpose notes and chords between keys
- Interval Calculator — find the interval between any two notes
- BPM Calculator — tempo for your musical projects