Bass tuner online
A free chromatic bass tuner that listens through your microphone. It is built for low notes — down to the B0 of a 5-string — and shows exactly how many cents each string is off.
Sound is analysed on this page and never leaves your browser.
How to tune a bass with this tuner
- Tap “Start tuner” and allow the microphone.
- Pick 4-string standard (E A D G), 5-string (B E A D G), drop D or half step down.
- Play an open string and let it ring for a second — low notes need a moment to settle.
- Tighten the string if the needle is left of centre, loosen it if it is right.
- When the display turns red and holds, move to the next string.
- Check the 12th-fret harmonic of each string for a final, very clean reading.
Standard bass tuning: E A D G
A 4-string bass uses the same notes as the four lowest guitar strings, one octave lower: E1 (41.2 Hz), A1 (55 Hz), D2 (73.4 Hz) and G2 (98 Hz). A 5-string adds a low B0 at 30.9 Hz below the E.
Those frequencies are low enough that a laptop or phone microphone hears mostly their overtones. This tuner is set up to look for very low fundamentals, but if a string reads one octave high, play it a little harder or use its 12th-fret harmonic.
Use harmonics for the steadiest reading
Touch the string lightly directly above the 12th fret (do not press it down), pluck, and lift your finger. The bell-like note is exactly one octave above the open string and much purer, so the needle settles faster and moves less.
Harmonics at the 5th and 7th frets let you compare neighbouring strings by ear: the 5th-fret harmonic of one string should match the 7th-fret harmonic of the next.
Drop D and lower tunings
Drop D lowers only the E string to D, giving you a low D for songs in D and D minor. Half step down tunes every string a semitone lower to match bands that play in E♭. Choose either one in the menu and the tuner targets the new notes.
- 4-string standard: E A D G
- 5-string: B E A D G
- Drop D: D A D G
- Half step down: E♭ A♭ D♭ G♭
Bass tuning tips
Pluck with your thumb or the pad of a finger. A soft, round attack has fewer overtones than a pick or slap, so the tuner locks on faster.
Tune with the volume up. On an electric bass, roll the volume and tone fully up if you play near an amp, and turn off effects such as octavers or chorus.
Tune in playing position. A bass neck flexes a little when you hold it. Tune sitting or standing the way you will play.
Retune after the first song. Heavy strings settle as they warm up under your hands and stage lights.
Bass tuner questions
Can a phone microphone hear a low B string?
Usually yes, through its overtones. If the reading is unstable, use the 12th-fret harmonic, which the tuner reads very reliably.
Does it work for an electric bass?
Yes. Play near your microphone unplugged, or let the mic hear your amp.
Is it free?
Completely. No account, no download, no ads — and the audio never leaves your browser.
Can I tune a 6-string bass?
Tune the low five strings with the 5-string preset and the high C (C3, 130.8 Hz) by switching Auto off and checking the note name.
Why does my bass sound out of tune higher up the neck?
That is intonation, set with the saddles on the bridge. A strobe tuner, like the one in the FRET app, makes it much easier.
Can I change the A4 reference?
Yes, from 432 to 446 Hz, below the tuner.