Note Frequency Converter
Note names, hertz, MIDI numbers and cents, tuned to your A4 reference.
Try before you buy.
- Free preview: the rules, dates and checks that apply to your figures, with every computed amount hidden.
- Locked until you unlock it: download and copy.
- Unlock: Pro pass, ₹179 for 30 days or ₹79 for 1 week, a one-time payment that never renews. Unlock: Pro pass, $5.99 for 30 days or $2.99 for 1 week, a one-time payment that never renews.
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About the Note Frequency Converter
Convert between a note name such as A4 or B♭3, its MIDI number and its frequency in hertz, in 12-tone equal temperament tuned to the A4 pitch you choose: 440 Hz, 432, 442, 415 or any other. A frequency also gives its nearest note and how many cents it is sharp or flat, and every result includes the sound’s wavelength in air at 20 °C and a frequency table of all 108 notes from C0 to B8 at your tuning.
The free preview shows the result rows with the values hidden; a Pro pass shows every value, with copy and text or JSON downloads.
How to use it
- Choose what you have: a note name, a MIDI note number or a frequency in hertz.
- Enter it; for a note or a MIDI number you can add a cents offset if the pitch is bent.
- Set the A4 reference pitch (440 Hz by default).
- Select Convert; with a Pro pass, copy the working and the full note table or download them as text or JSON.
Formula
In 12-tone equal temperament each semitone multiplies the frequency by 2^(1/12), and A4 is MIDI note 69, so a MIDI note n sounds at f = A4 × 2^((n − 69) ÷ 12); a cent is a hundredth of a semitone. Middle C (C4) is MIDI note 60. The wavelength uses a speed of sound of about 343 m/s, in air at 20 °C. Note numbers follow the MIDI 1.0 specification.
Limitations
- Only 12-tone equal temperament is calculated; just intonation and other tunings are not.
- The wavelength assumes air at about 20 °C (343 m/s); temperature and humidity change it. Nothing is played or listened to.
Privacy
On this device: nothing is sent
Every value is calculated on your device; nothing is uploaded or stored.
Frequently asked questions
What do I get without a pass?
Without a pass, Note Frequency Converter shows the rules, dates and checks that apply to your figures, with every computed amount hidden. Until you unlock it, the result can’t be downloaded or copied. A Pro, Premium or Ultimate pass, a one-time payment that never renews, unlocks the full result. The pricing page lists the passes and their prices.
What is A4 = 432 Hz?
An alternative tuning reference: every note sits about 31.8 cents lower than in standard 440 Hz tuning. Enter 432 as the A4 reference and the whole table follows.
How many cents are in a semitone?
A hundred. A frequency 30 cents above a note is closer to that note than to the next one, which is 70 cents away.
Which octave number is middle C?
In the scientific pitch notation used here, middle C is C4 (MIDI note 60), and the A above it is A4 (MIDI note 69).