# Note Frequency Calculator

URL: https://speedycalculator.com/calculators/other/note-frequency/
Last updated: 2026-10-25

> The note frequency calculator converts a MIDI note number (or a semitone offset from A4) into frequency in hertz using equal temperament with A4 = 440 Hz, and gives the wavelength in air.

## Inputs

- MIDI note number — Middle C (C4) = 60, A4 = 69.
- Reference pitch A4 (Hz)

## Results

- Frequency
- Wavelength in air (343 m/s)
- Octave

## Formula

```
f = 440 × 2^((n − 69) ÷ 12)
```

## Explanation

In twelve-tone equal temperament, each semitone multiplies frequency by the twelfth root of two.

### How to use the Note Frequency Calculator

- **MIDI note number** — Middle C (C4) = 60, A4 = 69.
- **Reference pitch A4**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

The MIDI number of A4 is 69; each step up or down is one semitone.

### Inputs explained

FieldWhat to enterMIDI note numberA number. Middle C (C4) = 60, A4 = 69.Reference pitch A4In Hz

### What each result means

- **Frequency** = [Reference pitch A4]×2^(([MIDI note number] - 69)÷12)
- **Wavelength in air (343 m/s)** = 343÷[Frequency]
- **Octave** = floor([MIDI note number]÷12) - 1

### Example values

How the main result changes when **MIDI note number** changes and everything else stays at the example values above:

MIDI note numberFrequency (Hz)3046.2494511060261.62675622.254901,479.9781208,372.018

## Worked example

Inputs — MIDI note number: 60; Reference pitch A4: 440 Hz.

Results — **Frequency = 261.626 Hz**; Wavelength in air (343 m/s) = 1.311 m; Octave = 4.

## FAQ

**What is middle C’s frequency?**
About 261.63 Hz with A4 = 440 Hz.

**What about A = 432 Hz?**
Change the reference pitch.

**What formula does the Note Frequency Calculator use?**
f = 440 × 2^((n − 69) ÷ 12).