What is 12-tone equal temperament?

It is the standard Western tuning system that divides an octave into 12 equal semitones. Each semitone is a frequency ratio of 2^(1/12) ≈ 1.05946, so 12 semitones exactly double the frequency (one octave).

What reference pitch should I use?

The modern standard is A4 = 440 Hz (ISO 16). Some orchestras and historical performances use A4 = 432 Hz, 415 Hz (Baroque), or 466 Hz. This calculator accepts any positive frequency as the reference.

How do I find notes more than one octave away?

Simply enter semitone values beyond ±12. For example, +24 is two octaves up, and -12 is one octave down. There is no limit on the semitone range.

What does the cents display mean?

One cent is 1/100th of a semitone. The calculator shows the exact cent offset so you can see how far a frequency deviates from the nearest equal-tempered note.

Can I convert MIDI note numbers to frequencies?

Yes. MIDI note 69 corresponds to A4. Enter your MIDI note number minus 69 as the semitone offset with A4 = 440 Hz to get the frequency.

Equal Temperament Calculator

Calculate the exact frequency of any note in 12-tone equal temperament from a reference pitch and semitone offset.

Reference Pitch

Reference Note

Semitone Offset (n)

Positive = higher pitch, negative = lower pitch

Quick Intervals

Result

Enter values and click Calculate

Full Octave Frequencies

Based on current reference

Calculate a note to see the octave table

Note	Frequency (Hz)	MIDI

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Summary

The Equal Temperament Calculator computes the frequency of any note in the 12-tone equal temperament (12-TET) system. By dividing the octave into 12 equally spaced semitones, each step multiplies the frequency by the twelfth root of 2 (approximately 1.05946). Enter a reference pitch such as A4 = 440 Hz and a semitone offset to instantly find the frequency of any note on the piano keyboard or beyond.

How it works

Set the reference pitch frequency (default: A4 = 440 Hz).
Select the reference note name or enter a custom frequency directly.
Enter the number of semitones above or below the reference (positive = higher, negative = lower).
The calculator applies the formula: f = f_ref × 2^(n/12) where n is the semitone interval.
Results show the target frequency in Hz, the note name, and the octave.
Use the note picker to explore all 88 piano keys at once.

Use cases

Tune instruments to a non-standard reference pitch (e.g., A4 = 432 Hz).
Verify synthesizer oscillator frequencies against theoretical values.
Teach or study music theory and acoustics.
Generate frequency tables for electronic music production.
Calculate detuning in cents between two pitches.
Build custom scale or chord frequency sets for algorithmic composition.
Check if a recorded note is in tune with a given temperament.
Convert MIDI note numbers to frequencies.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu