Online Piano Tuner

How to check your piano

1. Use a quiet room and turn off fans, air conditioning or a running TV.
2. Tap "Start listening" and allow microphone access. The sound is analysed on your device and never uploaded.
3. Hold your phone or laptop close to the piano: over the open lid of a grand, or near the top of an upright with the lid open.
4. Press one key firmly and let it ring. Start with A4 (the A above middle C), then check a few notes between C3 and C6.
5. After three or more notes in the middle of the keyboard, the tool gives an overall verdict based on the average deviation.

What the cents reading means

A cent is one hundredth of a semitone, so there are 1,200 cents in an octave. The needle shows how far the note you played is from the exact equal-temperament pitch: negative means flat (too low), positive means sharp (too high).

Within about ±5 cents a single note sounds in tune to most people. Beyond 10–15 cents the piano starts to sound sour with singers, other instruments or recordings, and at 20 cents or more the difference is obvious. Because a tuning works on the whole instrument, the average across many notes says more than any single key.

Why pianos go out of tune

A piano holds roughly 18–20 tonnes of string tension on a wooden soundboard and pin block. Wood takes on and gives off moisture, so the soundboard swells in humid weather (pitch rises) and shrinks in dry weather (pitch falls). In Israel, humid coastal summers, dry sharav days and air conditioning all push the tuning around.

New strings keep stretching for a year or two, moving the piano knocks the tuning out, and in older pianos the tuning pins may hold less firmly. A piano that hasn't been tuned for years usually ends up well below A440 overall, and then a simple tuning is not enough.

A440 and other reference pitches

A440 means the A above middle C vibrates 440 times per second. It was agreed internationally in 1939 and later published as the ISO 16 standard; before that, pitch varied widely between countries and orchestras (France's 1859 standard was A435).

Many orchestras today tune slightly higher, around A442–A443, and baroque ensembles often use A415. A432 is popular online but has no special acoustic properties. Pianos in Israel are normally tuned to A440, and a tuner can set another pitch on request: pick the matching reference above to check against it.

Why the bass and treble read a little off

Piano strings are stiff, so their overtones are slightly sharper than perfect multiples of the fundamental (inharmonicity). To make octaves sound clean, tuners stretch the tuning: the low bass is set a little flat and the high treble a little sharp of the theoretical frequencies. A well-tuned piano can read −10 to −20 cents at the very bottom and +10 to +30 cents at the very top, which is why the verdict only uses notes from C3 to C6.

Why tuning needs a professional

This tool tells you how far out your piano is; it cannot tune it. Most notes have two or three strings that must each be brought to pitch and then matched to each other, using a tuning lever (hammer), mutes and a trained ear. The pin has to be set so it stays put, not just turned until the reading looks right.

If the piano is far below pitch, raising it means adding tonnes of tension, and a tuner will often do a pitch raise first and a fine tuning after it. Old or rusty strings can snap, and a slipped lever can damage the pin block. Please don't try it yourself: a professional tuning is safer and lasts longer.

Limits of an online tuner

• A phone microphone hears the whole room, so background noise and echoes can make the reading jumpy.
• If the strings of one note are out of unison with each other, the note "beats" and the reading wobbles. That alone is a sign the piano needs a tuning.
• The tuner shows the nearest note. A piano that is more than half a semitone flat will show the note below with a sharp reading.
• The lowest bass notes have a weak fundamental and may be hard to read on small speakers and phone microphones.