Note Name to Frequency Converter (Concert Pitch Supported)

Convert between note names (C4, A4, etc.) and frequencies (Hz) for free. Switch the reference pitch (A4 = 440Hz, 442Hz, and more) and check tuning deviation in cents.

Last updated: 2026-09-06

Standard Pitch (A4 = 440Hz) Frequency Table by Note (Octaves 2-6)

Theoretical values calculated using 12-tone equal temperament. The highlighted A4 (440.00Hz) is the reference note.

Note	2	3	4	5	6
C	65.41	130.81	261.63	523.25	1,046.50
C#	69.30	138.59	277.18	554.37	1,108.73
D	73.42	146.83	293.66	587.33	1,174.66
D#	77.78	155.56	311.13	622.25	1,244.51
E	82.41	164.81	329.63	659.26	1,318.51
F	87.31	174.61	349.23	698.46	1,396.91
F#	92.50	185.00	369.99	739.99	1,479.98
G	98.00	196.00	392.00	783.99	1,567.98
G#	103.83	207.65	415.30	830.61	1,661.22
A	110.00	220.00	440.00	880.00	1,760.00
A#	116.54	233.08	466.16	932.33	1,864.66
B	123.47	246.94	493.88	987.77	1,975.53

How note names relate to frequency

Physically, pitch is a matter of frequency in hertz, but music handles it by note names such as C4 and A4. What binds the two together is the frequency of A4, set by international standard at 440 Hz. From that reference, every semitone upward multiplies the frequency by the twelfth root of two, so that twelve semitones make exactly double — one octave higher. This tool converts between note names and frequencies on that basis.

The reference pitch differs from one body to another: orchestras sometimes adopt 442 Hz or 443 Hz. Change the reference and every frequency is recalculated to match it. Going the other way, from a frequency to a note name, the tool shows how far the value sits from the nearest note in cents, so it also serves for checking tuning.

How to convert notes and frequencies

Settle on a reference pitch Ordinarily you can leave it at 440 Hz. If the ensemble or the instrument you are matching uses a different reference, switch to 442 Hz or enter a value directly.
Get a frequency from a note name Type the letter, then the accidental, then the octave number — “A4”, “C#5”, “Bb3”. The MIDI note number is shown alongside.
Get a note name from a frequency Enter the frequency you measured and the nearest note name appears, together with the distance from it in cents.
Read how far off you are The cent value is shown in colour: green means all but exact, amber a slight deviation, red a state that needs adjusting.

Tips for getting more out of it

Middle C on a piano is "C4" in scientific pitch notation, which corresponds to MIDI note number 60. Use this as a reference when comparing against instrument tuning charts or the note numbers shown in DAW software.
You can type a sharp as either "#" or "♯", and a flat as either "b" or "♭". Upper and lower case letters are treated the same.
When using "Frequency → Note Name" as a makeshift tuner, the deviation is shown in green when within 5 cents, yellow when within 20 cents, and red beyond that, so you can see how far off you are at a glance.
Since orchestras and opera houses use different reference pitches, switch the reference pitch dropdown to match the ensemble you're playing with (440Hz, 442Hz, 443Hz, etc.) before calculating.

Where converting notes and frequencies helps

Checking an instrument’s tuning

Enter a measured frequency and you see in cents how far it strays from the note you were aiming at — and whether to tighten or slacken.

Matching the pitch of the ensemble you play with

When performing with an orchestra that uses 442 Hz, you can see beforehand how the frequency of each note changes.

Setting up a synthesiser

Where an oscillator’s frequency is given directly, look up at once the figure that answers to the note you want. It serves for checking MIDI note numbers as well.

Adjusting audio equipment

When working on a particular range with an equaliser, knowing which note names that band covers gives your adjustments a clearer aim.

Terms about pitch

Reference pitch: The value fixed as the frequency of A4. The international standard is 440 Hz, though some bodies use 442 Hz and the like.
Cent: A unit of one hundredth of a semitone. Within five cents, most listeners are held to hear the same pitch.
Equal temperament: A tuning that divides the octave into twelve equal parts. Every key then sounds alike, at the cost of a slight departure from pure intervals.
Scientific pitch notation: The way of writing a note name with an octave number attached. Middle C on a piano is C4.
MIDI note number: A standard that expresses pitch as a number from 0 to 127. Middle C is 60, and each semitone adds one.
Octave: The interval at which the frequency exactly doubles. The two notes are heard as the same name at a different height.

Frequently Asked Questions

Following an agreement reached at an international conference in 1939, the International Organization for Standardization (ISO) formally adopted A4 = 440Hz as the international standard pitch in 1955, under the designation "ISO 16." Before that, reference pitches varied widely between countries and ensembles, which caused problems when performing with orchestras from other nations, making standardization increasingly necessary.

A slightly higher pitch around 442Hz keeps the strings under more tension, which is said to produce a brighter, more brilliant sound, a preference especially common among major European orchestras. This is also partly attributed to "pitch inflation," a historical tendency for reference pitches to creep upward as performance standards have risen over time.

A cent is a unit for measuring tiny differences in pitch, defined so that one semitone in equal temperament equals 100 cents. While a single cent is an extremely small difference, a trained ear can distinguish deviations of around 5 to 10 cents, which is why cents are used as a precise tuning indicator.

Equal temperament divides an octave into 12 equal parts so that every key sounds equally usable, and it is the modern standard tuning system. Just intonation, on the other hand, tunes specific chords to simple integer frequency ratios (for example, a perfect fifth is 3:2) so they sound as pure as possible, but the harmony breaks down when modulating to a different key. This tool calculates using the more versatile equal temperament.

Side Note — The Hidden History Behind the Number 440Hz

The reference "A4 = 440Hz" might seem like an obvious given, but the number itself has no particular scientific necessity. It is essentially the product of a political compromise: representatives from various countries agreed on it at an international conference held in London in 1939, and it was only in 1955 that the International Organization for Standardization (ISO) formally adopted it as "ISO 16." Before that, France used 435Hz while other regions used even higher pitches, and this lack of a common standard hindered international performing activity.

Interestingly, reference pitch still isn't fully unified today. Many prestigious European orchestras, including the Vienna Philharmonic and the Berlin Philharmonic, use 442Hz or 443Hz, an expression of a phenomenon known as "pitch inflation." Tightening the strings further adds tension and brilliance to the sound, and this desire to make a stronger impression on audiences is thought to have gradually pushed reference pitch upward over time.

Things get even more complex with historically informed performance on period instruments from the Baroque era. Records reconstructed from organs and tuning forks of the time show that A4 varied by region and era, ranging from roughly 392Hz to 415Hz, considerably lower than the modern standard. This is why early music ensembles today often use 415Hz (roughly a semitone below modern A4) — it reflects a deliberate effort at historical authenticity.

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