Online Tuning Fork: A 440 Hz
A 440 Hz is the reference pitch of Western music: the ISO 16 standard from 1975 fixes A4, the A just above middle C on the piano, at 440 vibrations per second. This page opens our tone generator already at 440 Hz with a sine wave, the clean sound of a metal tuning fork.
Where to play A 440 Hz on each instrument
A4 at 440 Hz is the reference in ISO 16. On each instrument below, the position shown sounds exactly that note, ready to compare with the tuning fork.
| Instrument | Where A4 (440 Hz) is |
|---|---|
| Guitar | 1st string (E4) at the 5th fret |
| Mandolin (G D A E) | Open A pair (2nd course) |
| Ukulele (G C E A) | Open 1st string |
| Violin and viola | Open A string |
| Piano | A above middle C (49th key) |
How to use it
- Turn the volume down and press Play: a continuous A at 440 Hz sounds. Press again to stop.
- Play the same note on your instrument along with the tone (the table shows where A4 sits on each instrument). If you hear a beating, a slow wah-wah that rises and falls, you are still out of tune.
- Turn the tuning peg slowly: the slower the beating, the closer you are. When it disappears, the string is at A 440.
- If your group uses another reference, tap 442 Hz or 432 Hz, below the volume. Settings has ÷2, which drops an octave to 220 Hz, and ×2.
Help and explanations
Use it to tune a guitar, ukulele, mandolin or violin by ear, to give a choir its starting note, or to check that your clip-on tuner is calibrated. It works in the browser on phones and computers, with no app and no sign-up.
Where A 440 is on your instrument
Guitar: the 1st string (high E) at the 5th fret is exactly A4, 440 Hz. The open 5th string is also an A, but two octaves lower (A2, 110 Hz); the harmonic at the 5th fret of that string rings at the same 440 Hz as the fork.
Mandolin in G D A E: the open A pair is A4 itself. Ukulele in G C E A: the open 1st string is A4. Violin and viola: the open A string, which is where the orchestra starts tuning. Piano: the A just above middle C, the 49th key on an 88-key piano.
Tuning by ear with beats
When two nearly identical notes sound together, the volume rises and falls as many times per second as the difference in hertz. If your string is at 438 Hz you hear two beats per second; at 439, one; at 440 the sound holds still. That is why a tuning fork works even for untrained ears: you don't need to know whether the note is sharp or flat, only to make the beating go away.
Start with the string slightly flat and come up slowly. If the beating gets faster as you tighten, you've gone past the target: back off. Once the A is in, tune the rest by comparison or with the guitar tuner.
Tuning forks, 440, 442 or 432 Hz
The tuning fork was invented in 1711 by John Shore, an English trumpeter. For centuries the A changed from city to city; in 1939 an international conference in London adopted A = 440 Hz, which ISO later confirmed. Tuners, apps and electronic instruments leave the factory on that reference.
Many orchestras tune a little higher, at 442 or 443 Hz, for a brighter sound; if that is your case, use the 442 Hz tuner. 432 Hz is a preference of some musicians, with no proven effect on health. What matters is that everyone in the group uses the same reference.
Tips
- With headphones, start at a very low volume: a continuous pure tone tires the ear quickly.
- Can't tell which of two As is higher? Compare briefly and rest: after a minute of the same tone your ear loses precision.
- Phone speakers reproduce low notes poorly: for ÷2 (220 Hz), use headphones or a speaker.
- To check a clip-on tuner, hold it near the phone playing 440 Hz: it should read A with the needle in the centre.
Frequently asked questions
What is a 440 Hz tuning fork for?
It gives an exact reference note, A4, from which instruments and voices are tuned. When everyone tunes to the same A, the group sounds in tune together.
What note is 440 Hz?
It is A4, the A just above middle C on the piano. That is why you often see it written as A440 or concert pitch A.
How do I tune a guitar with the online tuning fork?
Play A 440 and, at the same time, the 1st string at the 5th fret; turn the 1st string's peg until the beating disappears. Then tune the rest by comparison: the 2nd string at the 5th fret matches the open 1st, the 3rd at the 4th fret matches the open 2nd, and the 4th, 5th and 6th strings at the 5th fret match the next thinner open string.
How do I tune a mandolin or ukulele with it?
On a mandolin the open A pair is A4; on a ukulele it is the open 1st string. Tune it until the beating stops, then check the other strings with the mandolin tuner, which reads each one through the mic.
Can I use the tuning fork for my voice?
Yes: listen to the A, sing the same note and notice whether the two blend. Lower voices usually sing an octave below (220 Hz, the ÷2 button). To see on screen whether you're on pitch, use the vocal tuner.
440 Hz or 432 Hz: which should I use?
440 Hz is the international standard used by tuners and electronic instruments. 432 Hz is a choice some musicians make, with no proven effect on the body; use the same reference as your group.