How to Use the Piano Note Frequency Calculator
Every note on a piano has a frequency set by a fixed mathematical ratio. The 88 keys run from the lowest A0 (key 1) to the highest C8 (key 88), and at standard concert pitch, key 49 (A4) is defined as 440Hz. Enter a key number and a reference pitch (A4 value), and this calculator returns that note's exact frequency along with its neighboring semitones.
The math follows equal temperament tuning. Each semitone up multiplies the frequency by the 12th root of 2 (about 1.0595), and a full octave (12 semitones) exactly doubles the frequency. Because of this fixed rule, any key's exact frequency can be calculated from its key number alone.
440Hz isn't the only reference pitch in use. Some orchestras tune to 442Hz for a slightly brighter tone, and historically-informed baroque performances sometimes use a lower reference like 415Hz. Choosing the reference pitch that matches your tuner or performance context gives you the exact frequency relevant to your actual instrument.
Frequently Asked Questions
A 1939 international standard set A4 at 440Hz, and that's still the modern concert pitch reference today. This calculator defaults to 440Hz, but you can switch the reference if your orchestra tunes to 442Hz or another value.
One semitone changes frequency by a ratio of about 1.0595 (the 12th root of 2). The absolute Hz difference grows larger as you move to higher keys.