This free cello tuner shows an interactive scroll and pegbox — tap a peg to target that string, or let Auto mode detect it for you. Supports Standard and Baroque tuning.
RUNS ENTIRELY IN YOUR BROWSER · YOUR AUDIO IS NEVER RECORDED OR SENT ANYWHERE
Last updated: · Reviewed for accuracy against current browser APIs
Share:
Choose your tuning below, then click "Start Tuning."
Pick Standard CGDA, or Baroque for historical, lower-pitch performance.
Click "Start Tuning."
Allow microphone access when your browser asks.
Bow or pluck the lowest C string first.
Tune it before moving on to the other three strings.
Watch the meter.
Use the pegs for large adjustments in small, quarter-turn increments, or the fine tuners for small ones, until the needle centers.
Tune G, D, and A, then recheck all four.
Tuning one string can slightly shift the others, so a final pass over all four strings is always worth it.
How this tuner detects pitch
When you bow or pluck a string, this tool analyzes the sound through your microphone using an autocorrelation algorithm — it compares the waveform against slightly delayed copies of itself to find the point where they line up most closely, and that lag reveals the exact frequency you're playing. This runs entirely in your browser via the Web Audio API; your microphone audio is never recorded, uploaded, or sent anywhere, and it disappears the instant you close the tab.
Troubleshooting a jumpy or inaccurate reading
The needle won't settle, or jumps between notes
Background noise is the most common cause — a fan, a TV, or other instruments ringing nearby all confuse pitch detection. Mute any strings you're not testing and play a single, clean note rather than a chord.
It picks the wrong string
In Auto mode, a string that's very badly out of tune can land closer to a neighboring string's target pitch than its own, so the tuner locks onto the wrong one. Switch to manual string selection until it's roughly in range, then Auto mode will track it correctly from there.
Nothing registers at all
Check that microphone permission was actually granted — look for a blocked-mic icon in your browser's address bar — and confirm you're playing firmly enough for the microphone to pick up a clear signal above any background noise.
Standard cello tuning, and why it's built on fifths
Standard cello tuning is C2, G2, D3, A3 — written CGDA from the lowest string to the highest. Every string sits a perfect fifth from its neighbor, the same interval pattern used across the whole violin family, which is exactly why the traditional "tune in fifths" method (checking two adjacent open strings together and listening for that ringing harmony) works as a genuine technique in its own right, independent of any tuner.
String
Note
Frequency
C (thickest)
C2
65.41 Hz
G
G2
98.00 Hz
D
D3
146.83 Hz
A (thinnest)
A3
220.00 Hz
Fun fact: this is the exact same set of intervals as viola tuning, just a full octave lower — so a cellist looking to branch out to another instrument will find the viola an unusually easy place to start.
Tuning with pegs vs. fine tuners
If your cello is only slightly out of tune, reach for the fine tuners — the small screws mounted on the tailpiece — since they let you land precisely on pitch with minimal risk of overshooting. If a string is really off, you'll need the tuning pegs in the scroll's pegbox instead, but turn them gradually: at most a quarter turn at a time, since large, fast adjustments risk snapping a string.
A reliable technique when a string is badly out of tune: loosen it a few semitones below target first (for the low C string, drop it down to around A2 or B2), then slowly tighten it back up. While tightening a peg, press it inward toward the pegbox as you turn to keep it seated and stop it slipping. Once all four strings are roughly in place, go back through them again with smaller adjustments, then finish with the fine tuners for the last precise correction on each string.
The cello's range — wider than the human voice
Alongside instruments like the oboe and clarinet, the cello is often described as sounding closest to the human voice — but it actually covers considerably more ground than any singer could. The lowest open-string note is C2 at roughly 65 Hz, while with fingered notes on the highest string the cello can reach up toward A5, nearly 880 Hz. That range lets a single instrument act as both a bass and a soprano voice, which is part of why the cello carries so much of the emotional weight in orchestral writing.
Why won't my cello stay in tune?
Time. Strings gradually slacken when an instrument sits unplayed, leaving it sounding flat the next time you pick it up.
New strings. Fresh strings need a few days to settle into position; playing and retuning regularly during that window speeds up the process.
Temperature and humidity. A cello's wood body expands and contracts with the surrounding conditions, which changes string tension. Aim for around 70°F (21°C) with 35–50% humidity for stable storage.
Slipping pegs. Usually caused by the same temperature and humidity swings loosening the peg's friction fit in its hole.
An unadjusted bridge. If the bridge has started leaning toward the fingerboard, straighten it promptly, or have a luthier do it, since a warped bridge throws tuning off on its own.
Retuning before every session is completely normal. If tuning problems persist despite checking all of the above, it's worth having a luthier look the instrument over for underlying issues.
Fixing slipping pegs
A peg that won't hold its position is almost always a friction problem, not a broken instrument. Pegs and their holes rely on a snug friction fit to stay put, and that fit gradually loosens as temperature and humidity shift over time. Pushing the peg in firmly while turning it is a reasonable temporary fix, but doing this repeatedly can eventually wear the hole further. A more lasting solution is peg drops or peg compound, applied directly to the peg where it meets the pegbox — these products are specifically formulated to restore the right amount of grip without making the peg stick or squeak. In a pinch, a bar of soap rubbed lightly on the peg can work similarly. If slipping continues after that, it's worth having a luthier check whether the pegs or their holes need to be refitted.
Frequently asked questions
How do I tune my cello with this tool?
Choose your tuning, click Start Tuning, then bow or pluck a string. The closest peg highlights automatically, and the needle shows sharp or flat until the peg turns green.
What is standard cello tuning?
Standard cello tuning is C2, G2, D3, A3 — with each string tuned a perfect fifth apart from its neighbor. It's the same intervals as viola tuning, just a full octave lower.
Should I tune with the pegs or the fine tuners?
Use the fine tuners on the tailpiece for small adjustments when a string is only slightly off. If it's well out of tune, use the pegs instead, turning them gradually in quarter-turn increments to avoid snapping a string.
Which string should I tune first?
Most cellists tune the lowest C string first, then work upward through G, D, and A, checking all four again afterward since tuning one string can shift the others.
What is the cello's range?
A cello's open strings span from C2 up to A3, but with fingered notes its practical range runs from roughly C2 up to around A5 — wider than the human voice, and capable of covering both bass and soprano registers.
Why won't my cello stay in tune?
Common causes include strings slackening over time when the instrument isn't played, new strings still settling in, temperature and humidity changes affecting the wood, slipping pegs, or a bridge that has started leaning toward the fingerboard.
Is cello tuning the same as viola tuning?
The intervals are identical, but the cello sits a full octave lower. Viola tuning is C3-G3-D4-A4, while cello tuning is C2-G2-D3-A3.
Why do my cello pegs keep slipping?
Pegs slip when the friction fit between the peg and its hole wears loose from temperature and humidity changes over time. Peg drops or compound restore enough grip to fix it, and pressing inward while turning also helps.
Is my audio recorded or sent anywhere?
No. All detection happens locally in your browser using the Web Audio API. Nothing is uploaded, recorded, or stored.
More tools on ProDeviceTest
Practicing music rather than just tuning up? These run the same way — instant, no download, right in your browser.
ProDeviceTest