Note Frequency Hz Calculator: Convert Any Musical Note to Hz

Middle C (C4) is exactly 261.626 Hz in standard A440 equal temperament. It is MIDI note number 60 and sits at the center of the standard 88-key piano keyboard. Its wavelength at 20°C is approximately 1.311 meters and its wave period is approximately 3.822 milliseconds. Middle C is the most commonly referenced note in music education, notation, and instrument range descriptions. At A432 tuning, C4 is approximately 256.869 Hz; at A442, it is 262.614 Hz.

A440 was standardized by ISO 16 in 1955 after decades of inconsistency in concert pitch across countries and ensembles. Before standardization, A4 varied from 415 Hz (Baroque period) to over 460 Hz in some 19th-century orchestras. The 440 Hz value was chosen as a practical compromise reflecting the dominant practice in American recording and broadcasting in the mid-20th century. The American National Standards Institute (ANSI) adopted it, and it subsequently became the reference for electronic tuners, piano manufacturing tolerances, and all digital audio software in the United States. The NIST defines the hertz as one cycle per second, which is the unit in which all pitch frequencies are measured.

A cent is one hundredth of a semitone in equal temperament, used to measure very small pitch differences that are too small to describe in note names. One semitone equals 100 cents. Zero cents means the measured frequency is exactly in tune with the nearest note. Positive cents means the frequency is sharp (higher than the target pitch); negative cents means it is flat. Most human listeners detect pitch deviations of around 25 to 30 cents. Trained musicians can typically perceive 5 to 10 cents. Professional recording standards consider a performance within 5 cents of the target pitch as in tune. The formula for cents deviation is: cents = 1200 times log base 2 of (measured frequency divided by nearest note frequency).

In 12-tone equal temperament: f = A4 times 2 raised to the power of (n minus 69) divided by 12, where A4 is your reference frequency (440 Hz standard) and n is the MIDI note number. MIDI note 69 is A4, note 60 is C4 (Middle C), note 12 is C0, note 0 is C-1 (the lowest MIDI note at 8.176 Hz). To reverse-calculate: MIDI note = 12 times log base 2 of (frequency divided by A4) plus 69. The key relationship: every 12 semitones (one octave) exactly doubles the frequency. A3 is 220 Hz, A4 is 440 Hz, A5 is 880 Hz, A6 is 1,760 Hz.

A432 is 8 Hz lower than A440 at the reference pitch, which corresponds to a deviation of approximately 31.77 cents (about one third of a semitone flat). At C4 (Middle C), the difference is approximately 4.76 Hz. Proponents of 432 Hz claim it sounds warmer or more natural, but these claims are subjective and not supported by peer-reviewed acoustics research. The primary practical use of 432 Hz in US music is for artists who specifically want their music tuned to this reference for aesthetic or philosophical reasons. Some orchestras tuned to historical Baroque pitch use A415, which is a full semitone below A440. This calculator provides both A432 and A440 options for accurate conversions under either system.

For standard EADGBE guitar tuning: look up E2 (82.407 Hz), A2 (110.000 Hz), D3 (146.832 Hz), G3 (196.000 Hz), B3 (246.942 Hz), and E4 (329.628 Hz). Select each note in the calculator and click Play to hear the reference tone. Pluck the corresponding string and tune it to match. The sine wave tone in this calculator has no overtones, making it easier to match pitch by ear than a recorded guitar or piano. For drop D tuning, retune the low E string to D2 (73.416 Hz). For open G tuning (DGDGBD), look up D2, G2, D3, G3, B3, D4 in the table.

MIDI (Musical Instrument Digital Interface) is the protocol that connects digital instruments, DAWs, and hardware samplers. In MIDI, each pitch is represented by an integer from 0 to 127. MIDI note 69 is A4 = 440 Hz. MIDI note 60 is C4 (Middle C) = 261.626 Hz. Each increment of 1 in MIDI note number equals one semitone, and every 12 MIDI numbers equals one octave (frequency doubles). The conversion formula is: Hz = A4 times 2 to the power of (MIDI minus 69) divided by 12. Most DAWs including Ableton Live, Logic Pro X, Pro Tools, and FL Studio use this standard (called “scientific pitch notation”), where Middle C is C4 at MIDI 60.

Wavelength is the physical length of one complete sound wave cycle in air. At C1 (32.703 Hz), the wavelength is 10.49 meters: longer than most recording rooms. When a room dimension equals half the wavelength of a bass frequency, that frequency resonates in the room, creating a “room mode” that causes the frequency to be unnaturally loud at specific positions and inaudible at others. This is why bass in a poorly treated room sounds great at one spot (a resonance peak) and disappears a meter away (a null). Knowing the wavelength of the problem frequency helps you calculate the room mode and place bass traps in the appropriate corners. At 1 kHz (approximately B5), the wavelength is 34 centimeters: easier to treat.

A standard 88-key piano spans from A0 (27.500 Hz) at the lowest key to C8 (4,186.009 Hz) at the highest. This covers seven and a quarter octaves. The A0 lowest note approaches the lower limit of most people’s pitch perception (pure tones below approximately 20 to 30 Hz are more felt as vibration than heard as pitch). The C8 highest note is well within normal hearing range but is rarely used in standard piano literature. Extended pianos with 97 keys (such as those made by Bösendorfer) extend lower to F0 (21.827 Hz). The full harmonic content of a piano note extends well above these fundamentals, reaching several octaves of overtones that contribute to the piano’s characteristic timbre.

Many US professional orchestras tune above the ISO 16 standard of A440. Common practice: the New York Philharmonic has historically used approximately A442, as has the Los Angeles Philharmonic. Some European orchestras (Berlin Philharmonic, Vienna Philharmonic) have tuned as high as A444-445 Hz at certain periods. The reason is psychoacoustic: slightly higher pitch tends to sound brighter and more intense in large concert halls. The downside is incompatibility with organs (fixed-pitch instruments that cannot be retuned for a performance) and difficulty when collaborating with ensembles that use different references. The A442 and A443 options in this calculator allow you to calculate exact frequencies for these alternate standards.

At A4 = 432 Hz, Middle C (C4) has a frequency of approximately 256.869 Hz. This is calculated using the same formula: C4 is 9 semitones below A4 (MIDI 60 versus MIDI 69), so: f = 432 times 2 to the power of (60 minus 69) divided by 12 = 432 times 2 to the power of negative 0.75 = 432 times 0.59460 = 256.869 Hz. Interestingly, some 432 Hz proponents note that C4 at 432 tuning is approximately 256 Hz, which is a power of 2 (2 to the power of 8). This is numerologically interesting but acoustically irrelevant: equal temperament frequencies are irrational numbers at any reference pitch, and 256 Hz is only an approximation. Select A4=432 in this calculator to see all 120 notes at 432 Hz tuning.

Yes. The MIDI note number in the results panel maps directly to every major DAW and synthesizer: Ableton Live, Logic Pro X, Pro Tools, FL Studio, Reason, Cubase, and hardware synthesizers from Moog, Korg, Roland, Yamaha, and others. The Hz value maps to oscillator frequency settings in modular synthesizers (Eurorack), standalone synth editors, and sample editors where you need to specify a root note frequency rather than a note name. The wavelength value is useful when designing reverb tails and delay times: a reverb room size in meters relates directly to the wavelength of the notes being processed, affecting which frequencies resonate in the simulated space.

Human pitch perception begins to break down below approximately 20 to 30 Hz. Pure tones below 20 Hz (infrasound) are felt as vibration rather than heard as a pitched note. Most people can identify the pitch of notes from about E0 (20.602 Hz) upward, though this varies significantly by individual. The sub-bass range used in electronic music production (20 to 60 Hz, covering C0 to B2) is perceived partly as pitch and partly as physical body sensation. At 16 Hz (C0 in this table), virtually no one perceives a distinct pitch, though the vibration is physically noticeable. This is why organ pipes and synthesizers that produce notes below about 30 Hz are typically combined with octave-up overtones to create perceived pitch at the intended note.

In 12-tone equal temperament, C# and Db are two different names for exactly the same pitch, at exactly the same frequency. This is unique to equal temperament: in just intonation and many historical tuning systems, C# and Db were distinct pitches with slightly different frequencies, related to their different mathematical relationships in the key system. Equal temperament eliminated this distinction by making all 12 semitones exactly equal, which is why every keyboard instrument can play in all 12 keys without retuning. The choice between sharp and flat notation is a matter of musical context (C# makes more sense in the key of A major; Db makes more sense in the key of Bb minor) but the actual acoustic frequency played on a piano, guitar, or synthesizer is identical.

Yes, the Web Audio API tone generator works on iPhone (Safari and Chrome), Android (Chrome and Firefox), and all major mobile browsers. The sine wave plays directly through the device speaker or connected headphones without any audio file download. Some mobile browsers (particularly Safari on iOS) require the tone to be triggered by a user gesture (a tap or click), which is why the Play button must be pressed rather than the tone playing automatically. The tone duration is approximately 1.7 seconds with a short fade-in and exponential decay, mimicking the natural decay of a plucked string rather than an abrupt stop that can be startling at higher frequencies.

Yes. After calculating, click PDF Report to download a branded report that includes the selected note’s frequency, MIDI number, wavelength, and period; the full 12-note table for the current octave at your selected A4 reference; a set of key reference frequencies (A4, Middle C, all octave As, the piano range endpoints); and the complete US instrument frequency ranges. The WhatsApp share button sends a formatted text message with the note, frequency, MIDI number, wavelength, and a link to this tool. Both features are completely free and require no account or registration.