How is a frequency converted to a note name?

The number of semitones from A4 (440 Hz) is 12 times the base-2 logarithm of the frequency divided by 440. Rounding gives the nearest note, and the remainder, multiplied by 100, gives the cents deviation. The MIDI note number then maps to a name and octave.

Why is it useful to know the note of an EQ band?

Boosting or cutting a frequency that matches a strong note in the music sounds intentional and musical, while a band landing between notes can sound off. Knowing that 250 Hz is roughly B3 helps you relate a muddy build-up to the actual pitches causing it, especially on bass and vocals.

What note is A4 and why 440 Hz?

A4 is the A above middle C and the standard concert pitch reference at 440 Hz. All other equal-tempered note frequencies are derived from it by multiplying or dividing by the twelfth root of two for each semitone. Some orchestras tune to 442 or 443 Hz, but 440 is the global default.

What does the cents value mean?

A cent is one hundredth of a semitone, and 1200 cents make an octave. A cents reading near zero means your EQ frequency sits right on a note; a reading near plus or minus 50 means it falls exactly between two notes. Under about 10 cents is effectively on pitch.

Should I always tune EQ bands to notes?

Not always. Broad tonal shaping with wide Q does not need note alignment. But for narrow, surgical cuts of a resonance or a problem note, matching the band to the exact frequency of that pitch is far more precise than nudging by ear, and this converter gives you that frequency directly.

EQ Frequency to Note Name Converter

EQ plug-ins speak in hertz, but music speaks in notes. This converter bridges the two: enter any EQ frequency and see the nearest musical note, or enter a note and read back its exact frequency for a surgical cut. Making EQ moves that line up with the actual pitches in a track sounds more musical and intentional.

How it works

Equal temperament places A4 at 440 Hz and spaces every semitone by the twelfth root of two. To find the note for a frequency, the tool measures how many semitones it sits from A4:

semitones from A4 = 12 x log2(freq / 440)

Rounding to the nearest whole semitone gives the note; the leftover fraction, times 100, is the cents deviation (positive = sharp, negative = flat). The rounded value maps to a MIDI number and then to a note name and octave.

The reverse direction

Going from a note to a frequency is the inverse:

freq = 440 x 2 ^ ((midi - 69) / 12)

where MIDI 69 is A4. This gives the exact centre frequency to dial into a narrow EQ band when you want to cut or boost a specific pitch.

Why it helps mixing

A muddy low-mid build-up around 250 Hz is roughly B3; harshness near 3 kHz sits around F#7. Relating the numbers to notes makes it easier to reason about which pitches in the arrangement are causing a problem — especially with bass lines and vocal resonances, where a narrow cut tuned to the offending note removes the issue without dulling the whole region.

Worked example

Enter 440 Hz and you get A4, 0 cents — dead on. Enter 261.63 Hz and you get C4 (middle C), 0 cents. Enter 300 Hz and the nearest note is D4 (293.66 Hz) at about +37 cents, telling you that band falls between D4 and D#4 — useful to know before a narrow surgical cut.

All conversions run locally in your browser.