What this tuner tells you — and what it doesn’t
Be clear about the job before you start. A piano has around 230 strings across 88 keys, held at roughly twenty tons of combined tension, and each note is adjusted by turning a pin with a specialised lever. Tuning one properly is a professional trade, and a chromatic tuner is not a substitute for it — for reasons covered further down, a correctly tuned piano is deliberately not in exact equal temperament across its range.
What this page does very well is measure. Play a key and you get the note, the octave and the precise cents offset. That answers the questions that actually matter to an owner: is my piano still at concert pitch, how far has it fallen, is it worth recording with, and roughly what am I asking a technician to do?
- C4Middle C261.63 Hz
- C♯4277.18 Hz
- D4293.66 Hz
- D♯4311.13 Hz
- E4329.63 Hz
- F4349.23 Hz
- F♯4369.99 Hz
- G4392.00 Hz
- G♯4415.30 Hz
- A4Concert pitch reference440.00 Hz
- A♯4466.16 Hz
- B4493.88 Hz
Tap a tone to hear the target, then play the matching key and compare on the dial above. The extreme octaves may not reproduce on phone or laptop speakers — use the dial for those, not your ears.
The five-minute pitch check
- Start with A4 — the A above middle C. Play it firmly and read the dial. On a piano at concert pitch it lands on A with the needle near centre. This one note tells you most of what you need to know.
- Check middle C (C4), then an octave each way. Play C3, C4 and C5 and write down the cents for each. You are looking for the shape of the drift, not one number.
- Sample the extremes. Play something low in the bass and something up in the top octave. Do not be alarmed if these read further off than the middle — see stretch tuning below.
- Listen for unisons. Most notes on a piano use two or three strings tuned to the same pitch. If a single note wavers or sounds like a chorus effect, its strings have drifted apart from each other. The dial will hunt and refuse to settle on that note, which is itself a useful diagnosis.
| What A4 reads | What it means |
|---|---|
| Within ±5 cents | At concert pitch. A touch-up tuning at most. |
| 5–15 cents flat | Normal drift for a piano a year or so past its last tuning. |
| 15–40 cents flat | Several years untuned. Expect a technician to mention a pitch raise. |
| Around 100 cents flat | A full semitone down — the piano has been neglected for a long time and will need more than one visit to hold pitch. |
| Sharp | Unusual. Often a humidity swing rather than genuine drift; re-check in a week. |
Why a perfectly tuned piano still reads sharp and flat
This is the part that surprises people holding a tuner. Piano strings are stiff, and stiff strings are inharmonic: their overtones sit slightly sharper than exact whole-number multiples of the fundamental. Because we hear octaves by matching a note’s overtones against the note above, a piano octave that sounds right measures slightly wider than a mathematically exact 2:1.
Technicians therefore use stretch tuning: the top octaves are tuned progressively sharp and the bass progressively flat, relative to equal temperament. On a small piano the total stretch can reach 30 cents or more at the extremes. So if your top octave reads sharp and your bottom octave reads flat while the middle sits at zero, that is not a fault — that is a well-tuned piano, and a tuner that forced every note to zero would make it sound worse. Our guide to centscovers the measurement side of this.
Things you can usefully do yourself
- Document it.Record A4 and a handful of other notes with dates. A history of readings tells a technician far more than “it sounds a bit off”.
- Match another instrument to the piano. If the piano is 20 cents flat and it is not getting tuned before rehearsal, tune the guitars to it rather than to 440. The full-screen tuner lets you shift its reference pitch to do this.
- Check before you record. Five minutes with this page will tell you whether a session is going to fight the piano.
- Decide whether it is worth restoring. A second-hand piano that reads a semitone flat across the board is a bigger commitment than a bargain price suggests. Read it before you buy it.
Frequently asked questions
Can I tune my own piano with this?
Honestly, no — not to a good result. Beyond the tuning lever and mutes you would need, the skill is in setting a temperament by ear and stretching the octaves to suit that particular instrument, and neither is something a chromatic dial can guide you through. What you can do is measure precisely where your piano stands, which is genuinely worth knowing before you call anyone. Instruments where DIY tuning is realistic include the guitar, the kalimba and, with care, the accordion.
What frequency is middle C on a piano?
Middle C — C4, the C nearest the middle of the keyboard — is 261.63 Hz in equal temperament with A4 at 440 Hz. On a real piano the measured value will sit a few cents either side of that because of stretch tuning, and that is correct rather than wrong. Tap the highlighted C4 in the reference tones above to hear it.
How often does a piano need tuning?
Once or twice a year for a piano in a home, and considerably more often for one being recorded or performed on. New pianos need more attention in their first couple of years while the strings and frame settle. The real driver is humidity stability, not how much you play — an untouched piano in a room with swinging humidity will drift faster than a well-housed one played daily.
Why won't the tuner settle on a note?
Almost always because that note’s two or three strings have drifted apart from each other. The tuner hears several close pitches at once and hunts between them. It is a reliable way to find which notes have unison problems — play up the keyboard and note every key where the dial refuses to lock. Sustained pedal down and other notes still ringing will cause the same symptom, so check with everything else damped.