Press Play for A at 440 Hz, then pick a row: the same note, octaves higher or lower.
Octave Tone Generator: 440 Hz sine tone
Start with your device volume low.
Sine wave · both channels
Hz
Period 2.27 ms
Wavelength 78 cm (30.7 in)
The note A4
Ready. It starts quiet and fades in over half a second.
A steady tone can harm ears and speakers before it sounds loud. Hear nothing? Do not turn it up to find the tone: small speakers cannot play very low tones, and many adults cannot hear very high ones.
Percent of this tool's loudest. Your device volume does the rest.
Use this tone generator octave by octave: one note, A or C, in each of eight octaves across the piano. Each octave up doubles the frequency and each octave down halves it.
Read the full guide
Hear what an octave is
1. Press Play. The A at 440 Hz fades in at 10% volume.
2. Press A5, one octave over the tuning A: 880 Hz, twice the frequency. Then A3, the cello's top string: 220 Hz, half of it. All three sound like one note at different heights.
3. Carry on down the A rows at the same volume. The lowest row a speaker still plays shows how far down it reaches.
4. The C rows do the same, from the top key of a piano to its lowest C.
For the octave of any other pitch, type its frequency, then press ×2 to go up or ÷2 to go down.
Questions and answers
What is an octave in Hz?
A ratio of 2 to 1, not a set number of hertz. From A3 to A4 is 220 Hz; from A6 to A7, the same step to the ear, is 1,760 Hz.
How many octaves does a piano have?
A standard piano has 88 keys from A0, 27.5 Hz, to C8, 4,186.01 Hz: seven octaves and a minor third. That is why this page has eight As, A0 to A7, and eight Cs, C1 to C8.
Why do notes an octave apart sound alike?
Their harmonics are closely related, so the ear tends to hear both as the same note at another height. For that reason they share a letter name.
All 16 notes
A in eight octaves 8
A7, the highest A on a piano3,520 Hz, key 85 of 88. Eight times 440 Hz: three doublings, so three octaves over the tuning A.
A6, two octaves over the tuning A1,760 Hz, key 73. Four times 440 Hz: two doublings, so two octaves.
A5, one octave over the tuning A880 Hz, key 61, exactly twice 440 Hz: one doubling, so one octave.
A4, the tuning A440 Hz, key 49, the note this page opens on. The pitch standard, and a string of the violin and the viola.
A3, the cello's top string220 Hz, key 37, half of 440 Hz. A cello's four strings are C2, G2, D3 and A3.
A2, a guitar's fifth string110 Hz, key 25. A guitar in standard tuning runs E2, A2, D3, G3, B3, E4: this is its second lowest string.
A1, a double bass string55 Hz, key 13. A double bass is usually tuned E1, A1, D2 and G2. Silence here on a small speaker is normal.
A0, the lowest key of a piano27.5 Hz, key 1 of 88, four octaves under the tuning A. Numbered 0 because octave numbers change at C, and this A lies under C1.
Show all 16 notes (8 more)
C in eight octaves 8
C8, the top key of a piano4,186.01 Hz, key 88 of 88. Seven octaves above the lowest C: 128 times its frequency.
C7, three octaves over middle C2,093 Hz, key 76. Eight times the frequency of middle C: three doublings.
C6, soprano C1,046.5 Hz, key 64, two octaves above middle C. Known as soprano C, or high C.
C5, tenor C523.25 Hz, key 52, one octave above middle C. Known as tenor C.
C4, middle C261.63 Hz, key 40. Numbered 4 as the fourth C key of a standard 88-key piano.
C3, the viola's lowest string130.81 Hz, key 28, one octave under middle C. A viola is tuned C3, G3, D4 and A4, an octave above the cello.
C2, the cello's lowest string65.41 Hz, key 16, two octaves under middle C. Known as deep C.
C1, the lowest C on a piano32.7 Hz, key 4. Known as pedal C. A five-string double bass can reach it; small speakers cannot.