Note Frequency Calculator

Frequently Asked Questions

Why does each octave double the frequency?

Doubling frequency is a 2:1 ratio, the most consonant interval in music. Notes an octave apart share a name because they sound so closely related.

What is the 432 Hz vs 440 Hz debate?

Some people prefer a 432 Hz reference for aesthetic reasons. This calculator lets you test it instantly - it is purely a global pitch shift, not a different scale structure.

Why report the wavelength of a note?

A low E1 (about 41 Hz) has a wavelength over 8 metres, explaining why bass frequencies excite room modes. High notes have wavelengths of centimetres.

What is the difference between 12-TET and just intonation?

In 12-TET every semitone is an equal ratio of 2^(1/12). In just intonation, intervals use simple whole-number frequency ratios that differ from 12-TET by a few cents.

How accurate is the MIDI number returned?

It is exact and integer for the twelve named pitches in standard octave numbering. Pitch-bend or microtonal tuning adds a fractional offset on top.

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Estimates for informational purposes only.

Important Disclaimer: Estimates for informational purposes only.

This calculator provides estimates for informational purposes only. Results are based on assumptions and may not reflect actual outcomes. Consult qualified professionals in relevant fields before making important decisions based on these results.

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How It Works

Every pitch on a piano corresponds to a precise frequency in hertz. This calculator converts a note name and octave into that frequency using twelve-tone equal temperament (12-TET), the tuning system used by virtually all modern instruments. The reference is the concert pitch A above middle C - A4 - conventionally 440 Hz but adjustable here.

From A4 the calculator counts how many semitones away your chosen note sits and applies the equal-temperament ratio. It also returns the MIDI note number, the waveform period in milliseconds, and the acoustic wavelength in air, which tells you how big a resonator or room mode for that note really is.

In 12-TET each octave is split into twelve equal ratio steps: one semitone multiplies frequency by 2^(1/12). The frequency of a note n semitones from A4 is f = ref x 2^(n / 12). Wavelength is the speed of sound (about 343 m/s at 20 degrees Celsius) divided by f.

Use Cases

Note-to-frequency conversion is needed across many musical and technical applications:

Tuning a synthesiser oscillator to a known pitch without a reference instrument nearby

Setting a notch filter to the exact frequency of a hum or resonance on a specific note

Building a test tone or reference signal for acoustic measurement

Understanding room mode frequencies by comparing a bass note's wavelength to the room dimensions

Checking that a tuner reads the correct frequency for a non-standard A4 reference pitch

Tips

Orchestras sometimes use 442 or 443 Hz; historically-informed ensembles use 415 Hz. Adjust the A4 reference to match the ensemble you are working with.

C# and Db are enharmonic equivalents with the same frequency in 12-TET. Select the spelling that matches your context.

A low E1 (about 41 Hz) has a wavelength over 8 metres - this explains why bass frequencies excite room modes and are hard to treat acoustically.

Doubling frequency is always 1200 cents (one octave) regardless of register.

Just intonation intervals differ slightly from 12-TET. A 12-TET major third is about 14 cents sharper than the pure 5:4 ratio.

FAQ

Why does each octave double the frequency?

Doubling frequency is a 2:1 ratio, the most consonant interval in music. Notes an octave apart share a name because they sound so similar.

What is the debate around 432 Hz?

Some people prefer a 432 Hz reference for aesthetic reasons. The math here lets you test it instantly - it is purely a global pitch shift, not a different scale structure.

Why report the wavelength?

A low E1 (about 41 Hz) has a wavelength over 8 metres, which is why bass frequencies excite room modes and are so hard to tame acoustically. High notes have wavelengths of centimetres.

What is the difference between 12-TET and just intonation?

In 12-TET every semitone is an equal ratio. In just intonation, intervals use simple whole-number frequency ratios. Most just intervals differ from 12-TET by a few cents.

How accurate is the MIDI number?

It is exact and integer for the twelve named pitches. Pitch-bend or microtonal tuning adds a fractional offset on top of the integer note number.

Note Frequency Calculator

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