How many keys on a piano, and why 88

A standard piano has 88 keys, of which 52 are white and 36 are black. Grand pianos, upright pianos and full-size digital pianos all share that number, and the keys run from A0, the lowest note at the far left, to C8, the highest at the far right. Electronic keyboards and MIDI controllers are often smaller, most commonly with 76, 61, 49, 37 or 25 keys.

The lit keys on the keyboard above are one octave, from middle C (C4) up to B4: seven white keys and five black keys. A full-size piano is that 12-key unit repeated seven times, plus four extra keys at the ends.

How the 88 keys add up

Seven full octaves, C1 through B7, hold 7 × 12 = 84 keys. Three more keys sit below the first C, and one more sits above the last B:

The diagram shows the 12-key unit on its own, with every key named. The white keys play the natural notes, A to G, and the black keys play the sharps and flats between them, which is why each black key has two names; sharps and flats on the piano explains them. The only black key that stands alone is A#0/Bb0 at the bottom: it is the last key of a group of three whose first two keys fall below the end of the keyboard.

How the piano grew to 88 keys

The piano did not start with 88 keys. Its range grew for well over a century, as composers asked for more notes and makers learned to build stronger instruments:

• About 1700: Bartolomeo Cristofori's first pianos, made in Florence, spanned four octaves, C2 to C6: 49 keys.
• Late 1700s: the pianos Mozart wrote for covered about five octaves.
• 1790s to 1810: the firm of Broadwood stretched the range to five and a half octaves in the 1790s and six octaves by 1810, and Beethoven used the new notes in his later works.
• Mid-1800s: seven octaves, A0 to A7, became common. That is 85 keys, and some older pianos still have exactly this range.
• Late 1800s: makers added A#7, B7 and C8 at the top, and 88 keys became the standard that new pianos still follow.

Stronger construction made the later steps possible. Longer, tighter strings need a frame that can hold their tension, and the cast-iron frames and improved piano wire of the 1800s let makers keep adding notes. Since the late 1800s the standard has not moved. The bottom key, A0, vibrates 27.5 times per second, not far above the 20 Hz usually given as the lower limit of human hearing, and pianos built with extra keys have stayed rare.

Pianos and keyboards with more or fewer keys

A few instruments depart from 88 keys in either direction:

The Austrian maker Bösendorfer adds its extra keys in the bass only, and all of them are black, so a pianist can still spot where the usual keyboard begins. The Australian maker Stuart & Sons extends both ends; its 108-key Beleura spans nine octaves less one note, and in 2024 it delivered a piano with 112 keys.

How many keys smaller keyboards have

Each common keyboard size is a slice of the full piano. The ranges below are typical starting positions rather than fixed rules, since models differ and most keyboards can move their range by octaves.

What each size can play follows from its range:

• 88 keys play everything written for the piano.
• 76 keys lose only the seven lowest keys, A0 to D#1, and the five highest, G#7 to C8. Music that reaches those notes has to be played an octave higher or lower.
• 61 keys keep two octaves below middle C and three above it. That leaves room for both hands playing a melody and chords, but music that uses the bottom or top of the piano needs more keys.
• 49, 37 and 25 keys are sizes often found on MIDI controllers. They cover four, three and two octaves around middle C and reach other notes by shifting octaves, which the guide to piano octaves explains.

The beginner's buying guide covers which size suits which goal, and the keyboard layout guide maps the first and last key of each size.

Full-size keyboards and full-size keys

A keyboard with the full range of a piano has 88 keys. "Full-size" is also used for the keys themselves: keys as wide as a piano's, whatever their number. On a standard keyboard the seven white keys of one octave span about 6.5 inches (16.5 cm), so each white key is roughly 23.5 mm wide. Most electronic keyboards have keys close to that size, while some small keyboards and controllers use narrower mini keys.

Digital pianos are defined largely by their 88 weighted keys; instruments with fewer keys are usually called keyboards instead, although some compact and stage pianos have fewer keys, such as 73. To play all 88 keys without an instrument at hand, open a full 88-key piano in your browser on our companion site.