SuperTime Ultra

Convert a frequency to a note, or a note to Hz

Convert a frequency in Hz to the nearest musical note, with its cents offset and MIDI number, or turn a note into Hz. Set A4 from 400 to 480 Hz.

Type a frequency and the converter shows the nearest equal-tempered note, how many cents sharp or flat the frequency is and the MIDI note number. Switch direction to get the exact frequency of any note from octave 0 to octave 8. Both directions use the A4 reference you set, and you can play a short sine tone to hear the result.

What this tool includes

Hz to note

Enter any frequency from 1 Hz to 20,000 Hz. The result shows the note name, its octave, the offset in cents and the MIDI note number.

Note to Hz

Choose one of the 12 notes and an octave from 0 to 8 to see the frequency to two decimal places.

Adjustable A4 reference

A4 is 440 Hz unless you change it. Set any reference from 400 Hz to 480 Hz, such as 432 Hz, and every result updates.

Listen, or start from a common frequency

Play the frequency as a short sine tone. One tap fills in a common frequency, including middle C, A4, 60 Hz mains hum and a 1 kHz test tone.

How to use this tool

  1. Choose a direction with the two buttons at the top: Hz to note, or note to Hz.
  2. For Hz to note, type the frequency. The note, cents and MIDI number update as you type.
  3. For note to Hz, tap a note name and then an octave. Middle C is C4.
  4. Press the speaker button or Play to hear a short sine tone at that frequency.
  5. If you tune to a different A, change the A4 reference at the bottom of the tool before you read the results.

Practice tips

  • A cents value near zero means the frequency is close to an equal-tempered note. The value shows green at 0 cents, amber within 10 cents and red beyond that.
  • To name a hum or a room resonance, read its peak frequency from a spectrum analyser and type it in to see which note it is closest to.
  • Doubling a frequency raises it one octave and halving it drops it one. 220 Hz, 440 Hz and 880 Hz are all A.
  • Phone and laptop speakers reproduce little bass, so use headphones to hear very low tones.
  • Note names are written with sharps. A# is the same pitch as B-flat.

Frequently asked questions

How do you convert a frequency to a note?

Divide the frequency by the A4 reference, take the base-2 logarithm, multiply by 12 and add 69. That gives the MIDI note number. Rounding it gives the nearest note, and the part left over, times 100, is the offset in cents.

What frequency is middle C?

With A4 at 440 Hz, middle C (C4) is 261.63 Hz to two decimal places. Its MIDI note number is 60.

What are cents?

A cent is one hundredth of an equal-tempered semitone, so an octave has 1,200 cents. A positive value means the frequency is sharp of the nearest note and a negative value means it is flat. The converter rounds to whole cents, so the value stays between -50 and +50.

Can I use 432 Hz tuning?

Yes. Set the A4 reference to 432 and the converter recalculates every note and frequency from that pitch. Any reference from 400 Hz to 480 Hz works.

Which octave numbers does it use?

Scientific pitch notation, where middle C is C4 and the A above it is A4. A4 is MIDI note 69.