Bass tuner

Standard bass tuning is E A D G, from the thickest string to the thinnest: the same notes as a guitar's four lowest strings, one octave lower.

Lodestone for iPhone shows these strings too, with the one you're tuning lit up. 99¢, once.

Bass notes and frequencies

Diagram of bass tuning: four strings tuned E A D G, from the thickest string to the thinnest.

String	Note	Frequency
4th	E₁	41.20 Hz
3rd	A₁	55.00 Hz
2nd	D₂	73.42 Hz
1st	G₂	98.00 Hz

Frequencies use A4 = 440 Hz. Strings are numbered from the thinnest.

5-string bass: B E A D G

String	Note	Frequency
5th	B₀	30.87 Hz
4th	E₁	41.20 Hz
3rd	A₁	55.00 Hz
2nd	D₂	73.42 Hz
1st	G₂	98.00 Hz

Drop D bass: D A D G

String	Note	Frequency
4th	D₁	36.71 Hz
3rd	A₁	55.00 Hz
2nd	D₂	73.42 Hz
1st	G₂	98.00 Hz

The low E on a bass is E1, at 41.20 Hz. A 5-string bass adds a low B below it (B0, 30.87 Hz), and drop D lowers the E to D.

Turn on the mic and play a string. Phone and laptop mics hear low notes faintly, so play firmly and keep the bass close.

Tuning a bass

Tune the low E first. It's the deepest note, so give it a firm pluck.
Press the E string at the 5th fret and tune the open A to it. Do the same from A to D, and from D to G.
On a 5-string, tune the low B so that its 5th fret matches the open E.

Questions

Is bass tuned to E1 or E2?

E1. A standard bass's low E is E1 (41.20 Hz), an octave below a guitar's low E (E2, 82.41 Hz).

What are the notes on a 5-string bass?

B E A D G. The extra low B is B0, at 30.87 Hz.

Can I tune a bass with my phone?

Yes. Lodestone listens for notes down to a 5-string's low B. Play firmly, since small mics pick up the lowest notes more faintly.

More tunings

Standard E A D G B E
Drop D D A D G B E
Half step down E♭ A♭ D♭ G♭ B♭ E♭
D standard D G C F A D
Drop C C G C F A D
DADGAD D A D G A D
Open G D G D G B D
Open D D A D F♯ A D
Ukulele tuner G C E A
Violin tuner G D A E

Lodestone for iPhone

Open Lodestone and play. It's already listening. Pick your instrument to see its strings, with the one you're tuning lit up. 99¢, once. No ads, no accounts, no subscription.