Cello Tuner

How to tune your cello with this tuner

1. Start the tuner. Click Start tuner (or the big microphone button) and choose Allow when your browser asks for the microphone. Put your phone or laptop on the music stand or a chair 30–50 cm (one to two feet) from the cello.

   

2. Play the A string first. Bow the open A string with a long, steady stroke. The tuner recognises the string, shows the note, its frequency and how many cents it is off.
3. Follow the needle. Left of centre means flat — tighten the string. Right of centre means sharp — loosen it. Within 15 cents the hint changes to Almost, and in the green zone (within 5 cents) the string is in tune.

   

4. Tune D, G and C. Work down from A, one string at a time. If the tuner jumps between strings, click a string’s note to lock it, and click it again (or Auto-detect) to go back to automatic.
5. Check all four again. Changing one string shifts the tension on the others slightly, so go round once more. Each string that stays in the green zone gets a check mark, and when all four have one the tuner tells you All four strings are in tune.

   

Cello string notes and frequencies

The cello’s four strings are tuned in perfect fifths: C2, G2, D3 and A3, from lowest to highest — exactly one octave below the viola.

The values assume A4 = 440 Hz, which puts the cello’s A string at 220 Hz. If your orchestra tunes to 442 Hz, move the Reference pitch (A4) slider to 442 and every target updates. Pure fifths are about 2 cents wider than equal-tempered ones, so tuning down from A by ear leaves the C string about 6 cents below a piano’s C — choose Pure fifths from A if that is how you tune.

The low C vibrates at only 65 Hz, and built-in laptop microphones may struggle with it. The tuner can still find the pitch from the string’s overtones, but bow firmly and use a phone or an external mic close to the f-holes.

Pegs or fine tuners?

• Fine tuners are for small corrections of a few cents. Turn clockwise to raise the pitch and anticlockwise to lower it. Many cellos have one on the A string only; student instruments often have four.
• Pegs are for bigger changes, such as new strings or a string that has dropped a semitone. Turn slowly while pressing the peg into the pegbox so it doesn’t slip.
• If a fine tuner is screwed almost all the way in, back it out a few turns and bring the string up with the peg instead.
• Tune up to the note: if a string is sharp, take it slightly below the target and bring it back up. It holds its pitch better.
• After tuning, check that the bridge still stands straight and isn’t leaning towards the fingerboard.

Tuning by fifths with double stops

Once the A string is right, many cellists tune the rest by ear: bow the A and D strings together and adjust D until the fifth sounds smooth, without a pulsing “wah-wah” beat. Then do the same with D and G, and with G and C. Use the needle to confirm each string, or click Tone under a string to hear its reference pitch until you click again.

How often should you tune?

Tune every time you play and check again during long rehearsals — temperature and humidity changes make strings and pegs move. New strings stretch for a few days, so retune them often until they settle.

Cello tuner not working? Fix it step by step

1. Read the message on the tuner. If the status turns red and says Microphone access blocked, your browser or device is stopping the page from using the microphone. If it says Microphone is busy, another app is using it (go to step 4).

   

2. Allow the microphone in your browser. Click the icon to the left of the address bar, open Site settings (or Permissions) and set Microphone to Allow. Then reload the page and press Start tuner again.

   

3. Let your browser use the microphone. Windows 11/10: Settings › Privacy & security › Microphone — turn on Microphone access and Let desktop apps access your microphone. Mac: System Settings › Privacy & Security › Microphone — turn on your browser, then quit and reopen it. Android: Settings › Apps › Chrome › Permissions › Microphone. iPhone and iPad: Settings › Apps › Safari › Microphone (iOS 17 and earlier: Settings › Safari › Microphone) — choose Ask or Allow.
4. Close apps that may be holding the mic, such as Zoom, Teams, a recording app or another tuner app, then press Start tuner again. If you have more than one microphone, pick the right one in the menu at the top right of the tuner.
5. No clear note? If the tuner says We can’t hear a clear note yet and the Input bar stays short or grey, the microphone hears too little. Move it closer to the f-holes, bow with more weight and raise the input volume in your system sound settings. If that doesn’t help with the C string, try your phone or a USB mic. If the bar is long but there is still no reading, reduce background noise and play one open string at a time.

   

6. Wrong octave on the low strings. Strong overtones can make a tuner hear C3 instead of C2. Lock the string you are tuning — readings one octave off are then folded back to it. If the needle jumps around, keep the bow speed even and stop the other strings from ringing.
7. Reference tone problems. Wear headphones if you play a tone while the tuner listens, otherwise it hears the tone instead of your cello. Phone and laptop speakers barely reproduce a 65 Hz C, so keep the reference tone on Warm — its overtones carry the pitch. No sound on iPhone: switch off Silent mode and turn up the volume.

About this cello tuner

This free online cello tuner runs entirely in your browser with the Web Audio API. Pitch is measured on your own device with the McLeod pitch method, using a longer listening window so the low C reads steadily. Nothing is recorded, uploaded or stored.

It works on Windows, macOS, Linux, ChromeOS, Android, iPhone and iPad in current Chrome, Edge, Firefox and Safari — no app or download needed.

Frequently asked questions