Why is 440 Hz the standard?

A4 = 440 Hz was standardized by the International Organization for Standardization (ISO 16) in 1955 to ensure consistent tuning across different countries and instrument manufacturers. Before this, concert pitch varied widely from 415 Hz (Baroque) to 452 Hz (some 19th-century orchestras).

What note is A4 in Hz?

A4 is 440.0 Hz in standard tuning. A4 is the A above middle C (C4 = 261.63 Hz). It is used as the reference frequency for all other notes: each semitone above A4 multiplies by the 12th root of 2 (approximately 1.0595), and each semitone below divides by the same factor.

What is the difference between 440 Hz and 432 Hz?

440 Hz is the international standard. 432 Hz is an alternative tuning where A4 is lowered by approximately 31.8 cents (just under one third of a semitone). All notes shift down by the same ratio (432/440). 440 Hz is used for all commercial music production and live performance; 432 Hz is a personal or artistic preference with no scientific evidence of perceptual superiority.

BeatKey Tools • Note Frequency Calculator

440 Hz Tuning Standard

Q: What is 440 Hz tuning?

440 Hz tuning means A4 (the A above middle C) is set to 440 Hz. It has been the international standard pitch since the ISO 16 standard was adopted in 1955 and is used by orchestras, recording studios, electronic tuners, and virtually all modern instruments worldwide.

A4 = 440 Hz is the international concert pitch. Every orchestra, studio, tuner, and DAW uses this reference. Here is why it was chosen and what it means for producers.

440 Hz

A4 reference pitch

1955

ISO 16 adopted

+31.8c

above 432 Hz

Global

standard since 1939

What Is 440 Hz Tuning?

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A4 = 440 Hz

The A note above middle C vibrates at exactly 440 times per second. Every other note is calculated relative to this.

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ISO 16 Standard

The International Organization for Standardization adopted A4 = 440 Hz as ISO 16 in 1955. Before this, pitch varied widely by country and era.

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Universal Reference

Every electronic tuner, DAW, synthesizer, and sample library defaults to A4 = 440 Hz unless you explicitly change it.

The Math Behind 440 Hz

440 Hz means A4 oscillates 440 times per second. Starting from A4, each octave up doubles the frequency, and each octave down halves it:

A3 = 220 Hz (440 / 2)
A4 = 440 Hz (reference)
A5 = 880 Hz (440 x 2)
A6 = 1760 Hz (440 x 4)

Each semitone within an octave multiplies by the 12th root of 2 (approximately 1.0595). So A#4 = 440 x 1.0595 = 466.16 Hz, and G#4 = 440 / 1.0595 = 415.3 Hz.

History of Concert Pitch 440 Hz

Baroque Era (1600s-1750s)

Concert pitch varied from around 392 Hz (A4) to 466 Hz depending on the region, instrument type, and era. Bach and Handel wrote for different pitches. Organs were often tuned higher than chamber music ensembles.

19th Century (1800s)

Pitch crept upward as instrument makers competed for brighter sound. Some orchestras reached 452 Hz. This put strain on singers and period instruments. The Paris Conservatoire tried to standardize at 435 Hz in 1859.

1939: International Standard

An international conference in London agreed on A4 = 440 Hz as the broadcasting standard. The BBC adopted it for radio broadcasts. World War II interrupted wider adoption.

1955: ISO 16 Ratified

The International Organization for Standardization formally ratified A4 = 440 Hz as ISO 16. Confirmed again in 1975. This became the global standard used by every instrument manufacturer, recording studio, and electronic tuner.

Today

440 Hz is the global default. Some orchestras (particularly in Germany and Austria) still occasionally use 442 or 443 Hz for a slightly brighter sound. Individual artists sometimes choose 432 Hz for personal preference. But 440 Hz remains the universal default for all commercial production.

Note Frequency Chart at 440 Hz

All note frequencies calculated relative to A4 = 440.0 Hz using equal temperament (12-TET).

Note	MIDI	Hz (440 standard)	Production Note
C4	60	261.63 Hz	Middle C
C#4 / Db4	61	277.18 Hz
D4	62	293.66 Hz
D#4 / Eb4	63	311.13 Hz
E4	64	329.63 Hz
F4	65	349.23 Hz
F#4 / Gb4	66	369.99 Hz
G4	67	392.00 Hz
G#4 / Ab4	68	415.30 Hz
A4	69	440.00 Hz	Concert A / Reference
A#4 / Bb4	70	466.16 Hz
B4	71	493.88 Hz
C5	72	523.25 Hz

See the full 128-note MIDI chart: MIDI Note Chart and Note Frequency Chart.

Key Production Reference Notes (440 Hz Standard)

The most important frequencies for producers, engineers, and musicians working at A4 = 440 Hz.

Note	MIDI	Hz	Common Use
A1	33	55.00 Hz	Deep bass, 808 fundamentals
A2	45	110.00 Hz	Bass guitar open A string
A3	57	220.00 Hz	Viola, guitar reference note
A4	69	440.00 Hz	Concert pitch reference, orchestral tuning
A5	81	880.00 Hz	High strings, flute upper range
A6	93	1760.00 Hz	Whistle, piccolo, upper EQ range
C4	60	261.63 Hz	Middle C, piano reference point
C1	24	32.70 Hz	Sub bass, 808 root note (low)

440 Hz vs 432 Hz: What Is the Difference?

Feature	440 Hz Standard	432 Hz Alternative
A4 frequency	440.00 Hz	432.00 Hz
Difference	Reference (0 cents)	-31.8 cents (slightly flat)
Standard status	ISO 16, universal default	Personal preference, not standardized
DAW default	All DAWs default to 440	Requires manual change to 432
Collaboration	Universal, no issues	Must communicate non-standard tuning to collaborators
Scientific evidence	Internationally ratified standard	No peer-reviewed evidence of perceptual superiority
Historical use	All modern recordings since 1955	Pre-20th century variable pitch, modern personal choice
Sample library compatibility	All sample libraries tuned to 440	Samples must be pitch-shifted to match

Bottom Line for Producers

Use 440 Hz for all commercial work. It is the default for every DAW, every sample library, and every collaborator you will work with. If you want to explore 432 Hz for personal or artistic reasons, use BeatKey's chromatic tuner to verify your actual tuning frequency.

Other Concert Pitch Standards

While 440 Hz is universal, some ensembles and genres use slightly different reference pitches:

A4 = 415 Hz

Baroque

Historical Baroque pitch (Versailles pitch). Used by period instrument ensembles playing Bach, Handel, Vivaldi on authentic instruments. Approximately one semitone below modern standard.

A4 = 432 Hz

Alternative

Promoted by some musicians as a "natural" or "healing" tuning. No scientific basis for claims of superiority, but used by some artists as a personal preference. See our 432 Hz guide.

A4 = 442 Hz

Orchestral

Some European orchestras (particularly German and Austrian) tune slightly higher at 442 or 443 Hz for a brighter sound. Common in professional chamber music contexts. Berlin Philharmonic has used 443 Hz.

A4 = 444 Hz

Crystal Bowl Tuning

Some sound healing and meditation practitioners use 444 Hz, claiming C4 = 528 Hz in this system (known as "528 Hz healing frequency"). No peer-reviewed evidence supports therapeutic claims.

How to Verify 440 Hz Tuning with BeatKey

Standard tuners show note name and cents deviation but DO NOT show the actual Hz value. BeatKey's chromatic tuner shows the exact Hz reading in real time, letting you verify your instrument is truly at 440 Hz and not drifting.

Why Hz Display Matters for Verification

Standard tuners say:

A4 | 0 cents | In tune

Cannot tell if you are at 440 Hz or 441 Hz

BeatKey shows:

A4 | 440.0 Hz | 0 cents | In tune

Exact Hz confirms you are at 440.0 Hz

Open BeatKey Chromatic Tuner

Go to notes.beatkey.app/tuner. Click "Start Tuning" and allow microphone access.

Play Your Reference Note

Play A4 (the A above middle C) on your instrument, keyboard, or tuning fork.

Read the Hz Display

BeatKey shows the detected Hz value in real time. For standard tuning, you should see 440.0 Hz (or very close to it).

Check the Cents Meter

The cents meter shows deviation from the nearest note. 0 cents at A4 = exactly 440 Hz.

Adjust If Needed

If your instrument shows 438 or 442 Hz, use your tuning peg, electronic tuner, or DAW pitch settings to correct to 440 Hz.

Frequently Asked Questions About 440 Hz

Does 440 Hz sound better than 432 Hz? ▼

There is no peer-reviewed scientific evidence that 440 Hz sounds better or worse than 432 Hz to human listeners. The difference is 31.8 cents, less than one third of a semitone. Most people cannot reliably distinguish between the two in blind tests. The choice is personal or artistic, not scientifically determined.

Why do some orchestras use 442 or 443 Hz? ▼

Some European orchestras tune slightly above 440 Hz (442 to 443 Hz) because higher pitch produces a slightly brighter, more brilliant sound from string instruments. The Berlin Philharmonic and Vienna Philharmonic have both used pitches above 440 Hz at various times. 440 Hz remains the ISO standard, and these orchestras deviate intentionally.

Is all commercial music recorded at 440 Hz? ▼

The vast majority of commercial recordings since 1955 are at or very close to 440 Hz, as this is the default for all DAWs, sample libraries, and synthesizers. Individual artists may tune slightly differently, and some genres (like some baroque revival recordings or new-age music) intentionally use other reference pitches.

How do I change my DAW to a different reference pitch? ▼

In FL Studio: Options > Project Settings > Concert Pitch (change from 440). In Ableton Live 12: Preferences > Link/Tempo/MIDI > Concert Pitch. In Logic Pro: Project Settings > Tuning > Concert Pitch. In Pro Tools: Setup > Session > Pitch A. Most DAWs default to 440 Hz and require a manual change to use any other tuning standard.