Convert Hz to MIDI Note: Formula, Chart and Cents

To convert Hz to MIDI note numbers, use MIDI = 69 + 12 × log2(frequency ÷ 440): the whole number is the nearest note and the decimal part × 100 tells you how many cents sharp or flat the frequency is. To go the other way, frequency = 440 × 2^((MIDI − 69) ÷ 12). The free pitch to Hz and MIDI converter does both instantly, including cents offsets and custom A4 tuning.

How MIDI note numbers work

MIDI describes pitch as a number from 0 to 127, one number per semitone. Middle C is 60 and A4, the 440 Hz tuning reference, is 69. Moving up one semitone adds 1; moving up an octave adds 12. Because the scale is logarithmic in frequency but linear in note numbers, MIDI numbers are the easiest way to do pitch maths: transposing by a fifth is always +7, whatever the starting note.

Note	MIDI number	Frequency (A4 = 440 Hz)
C1	24	32.70 Hz
A1	33	55.00 Hz
C2	36	65.41 Hz
C4 (middle C)	60	261.63 Hz
A4	69	440.00 Hz
C5	72	523.25 Hz

For a full list of every piano key, see our note to frequency chart, or open the chart view in the converter.

The formula, step by step

Here is a worked example converting 100 Hz:

1. Divide by 440: 100 ÷ 440 = 0.2273.
2. Take log base 2: log2(0.2273) ≈ −2.138.
3. Multiply by 12: −2.138 × 12 ≈ −25.65.
4. Add 69: 69 − 25.65 = 43.35.
5. Round to the nearest whole number: 43, which is G2 (98.00 Hz).
6. The leftover 0.35 × 100 = 35 cents, so 100 Hz is G2, 35 cents sharp.

If the leftover is above 0.5, round up instead and the cents become negative (flat). The converter handles this for you and shows the nearest note and the offset directly.

What are cents?

A cent is one hundredth of a semitone, so there are 1,200 cents in an octave. Cents let you describe tuning more finely than note names. Small differences of a few cents are hard to hear on one note but become audible as beating when two notes play together. In the converter you can add a cents offset to any note to see the exact frequency of a detuned pitch.

Why producers convert between Hz and notes

• Tuning kicks and 808s. Find the fundamental of a kick or 808 with a spectrum analyser, convert it to a note, and tune the sample to the song’s key. A kick with its fundamental at 55 Hz is sitting on A1.
• Setting EQ on musical frequencies. If a resonance rings at a frequency that matches the key, it may be a note you want to keep; if it is between notes, it is more likely a room or instrument problem. Our EQ frequency chart shows which ranges matter for each instrument.
• Tuning delay and filter settings. Pitched filter cutoffs and resonant effects can be set to a note so they reinforce the harmony.
• Programming synths. Some synths and modular gear show oscillator pitch in Hz; converting to notes keeps patches in key.

Changing the A4 reference

All of these numbers assume A4 = 440 Hz. If you work at 442 Hz, 432 Hz or another reference, replace 440 in both formulas with your value. In the converter, change the A4 reference and every result updates. MIDI numbers do not change with tuning; only the frequencies attached to them do. Read more in our explainer on A440 tuning.

Why does my DAW call middle C “C3”?

There are two naming conventions for octaves. The converter uses C4 = MIDI 60, the scientific pitch notation used by most music theory books. Ableton Live, FL Studio and some other DAWs label the same note C3. The MIDI number (60) and the frequency (261.63 Hz) are identical; only the octave label differs. If your notes seem an octave off when moving between tools, this is almost always why.

Worked example: tuning an 808 to the song

Suppose your track is in F minor and your 808 sample shows its fundamental at about 50 Hz on a spectrum analyser. Run 50 Hz through the formula: 69 + 12 × log2(50 ÷ 440) ≈ 31.35. The nearest note is MIDI 31, which is G1, and the sample is about 35 cents sharp of it. F1 is MIDI 29, so the sample needs to come down two semitones and 35 cents. In a sampler, set the coarse tune to −2 and the fine tune to −35 cents, and the 808 will now play F1 when you press the F key.

The same check works for kicks, toms and tonal percussion. A drum that sits between two notes can sound slightly off against the bass even when nothing is obviously wrong, and converting its pitch to a note makes the fix exact instead of guesswork.

Common mistakes

• Mixing octave conventions. Check whether a tool calls middle C “C3” or “C4” before you copy note names.
• Measuring a harmonic instead of the fundamental. Spectrum analysers often show louder harmonics. The fundamental is the lowest strong peak.
• Forgetting the tuning reference. A frequency that is “in tune” at A440 is a few cents off at A442.
• Rounding too early. Keep the decimals until the end so the cents value is accurate.

FAQ

Explore more MIDI topics in our MIDI and hardware guide, and see the MIDI Association specifications for the protocol itself. For instant answers, use the free pitch to Hz and MIDI converter.