Our Research   by   David Steinbuhler                                            

The opportunity to observe how hands of every size respond to a complete range of piano keyboard sizes led to the establishment of two additional piano keyboard standards.

   From 1998 to 2005 Steinbuhler & Company (which in 2018 became the DS Standard Foundation) extended an invitatHosts Linda & David Steinbuhlerion to pianists to come to Titusville, Pennsylvania and discover what size piano keyboard was most comfortable for them. Looking back at the activity that took place in our showroom, we now realize that it constituted vital research. As far as we know there has been no other comparable research in the 300 year history of the piano.
   The hands we observed were ones that had reached maturity, both male and female.  The pianists who came were motivated by the desire to find the keyboard size that best suited them. The environment we provided was one of relaxed comfort. There were rooms where they could spend the night.  In an uninterrupted afternoon or an entire weekend they worked with keyboards of every size.
   In addition to a Steinway B that was fitted with a complete range of keyboard sizes, we provided other pianos with conventional as well as smaller keyboards, which gave the pianists the freedom to experiment by moving from one to another.  Also, as they desired, we would change the keyboard in the Steinway B to one that was slightly smaller or slightly larger.  Our primary objective was to determine how many additional standards we should recommend and what sizes they should be.

Our Method
   For the purposes of this discussion, we will refer to the size of the keyboard by its Keyboards for the Steinway Boverall width and assume that it has 88 keys.  The average modern conventional keyboard measures just over 48”. The first keyboards we built were 42” in width.  By 1998 we also had keyboards that measured 39” and 45”.
   With these three additional keyboard sizes to work with, we immediately learned that there was strong interest in more than just one additional size. The great relief experienced by the 42” keyboard was accompanied by a desire to go smaller. There were also those pianists who desired relief from the pain and strain they experienced playing the conventional piano, but found the 42” keyboard too small.  It quickly became very clear that we needed at least two more keyboard sizes in addition to the conventional keyboard.
   To determine the size of two additional standards, our next step was to do a thorough study at the small end of the range.  For this we built 5 keyboards that measured 38, 39, 40, 41 and 42 inches. After establishing a practical small size, we would then add the appropriate in-between size.

The Results
   When does the keyboard become too small?  One pianist told me she wanted to “walk 10ths like Oscar Peterson” and to do this had calculated she would need a 38” keyboard.  She flew all the way across the country to try our smallest keyboards only to discover that they were too cramped for her.
   There was always the secondary consideration of the width of the sharps and the tradeoff that exists between the landing area on the sharp’s top and the space between them. After some experimentation, we found it prudent to keep close to the natural/sharp ratio found on conventional keyboards.
   Measuring dozens of hands, comparing them to the full range of hand sizes found in mature pianists, listening to feedback, and seeing what size keyboards were purchased soon led us to an appropriate small size.  For pianists whose hand spans are in the 7” to 8” range there was a desire to go smaller than the 42” keyboard as everyone wants to play 10ths comfortably.  But once they went below a 40” keyboard the space between the sharps was becoming too confined for all but the smallest hands with thin fingers. It became clear that the 41” keyboard was the best overall choice even though 10ths were still out of reach for the smallest hands.
   We were now ready to establish standards for a complete range of piano keyboard sizes. Because pianos and electronic keyboards will use differing numbers of keys, we decided to use the size of the octave to specify the size and nomenclature for the standards. Using the definition for the size of an octave as the distance from the center of one C key to the center of the next C key, which is the same as the distance form the left side of one C key to the left side of the next C key, we found that all piano keyboards in use today will hover around a 6.5 inch octave.  We also found that the octave size of all conventional pianos will stay within a .04 inch range of that number.  We therefore set the standard for the conventional keyboard octave at 6.50 inches with a tolerance of ± .04 inches.
   To find the appropriate size for the middle keyboard it is clear that the ratio between the conventional keyboard and the middle keyboard needs to be the same as the ratio between the middle keyboard and the keyboard at the small end of the range. The use of the ratio 48/52 gave us very attractive properties. Most importantly, it gave us a keyboard whose overall width was slightly larger than 41 inches, and we made it the ratio between our standard keyboard sizes. In addition to the three keyboards for adult pianists, we also added another forth keyboard the next size down for small children.
   Since most of the world uses the metric system we created two sets of standards, one expressed in inches and one expressed in centimeters. These two sets of standards taken together comprise the DS Standard®.    To learn about the origin of this trademark see Our Story.


The DS Standard®     The Donison-Steinbuhler Standard




Actual Octave size in Inches

Overall Width for 88 Keys



Conventional Keyboard

6.50 ±  .04 or 6.46 to 6,54




Universal Keyboard

6.00 ±  .04 or 5.96 to 6.04




7/8th Keyboard

5.54 ±  .04 or 5.50 to 5.58




Child’s Keyboard

5.11 ±  .04 or 5.07 to 5.15





Actual Octave size in Centimeters




Conventional Keyboard

16.5 ±  .1  or  16.4 to 16.6




Universal Keyboard

15.2 ±  .1  or  15.1 to 15.3




7/8th Keyboard

14.1 ±  .1  or  14.0 to 14.2




Child’s Keyboard

13.0 ±  .1  or  12.9 to 13.1


The nomenclature reflects the first two digits of the octave’s actual size.  The first set is expressed in inches and the second set is expressed in centimeters.

The octave of conventional keyboards found around the world will hover very close to a 6.50 inch octave but will not exceed the tolerance of ± .04 inches. We have therefore adopted this to be the tolerance for all the octave sizes. In the set that is expressed in centimeters, this tolerance is ± 1 millimeter.

A very accurate measurement for a piano keyboard’s octave can be obtained by measuring the distance from the left side of the piano’s first C key to the left side of the 7th C key and dividing this number by 7. Likewise, the 7-octave span of a keyboard with a 6.00 inch octave will measure exactly 42 inches.

The percentage jump from one keyboard size to the next keyboard size is always the same and is defined by the DS Standard Ratio™ which is equal to 48/52 ≈ .923  Multiply any octave size in the DS Standard® by this ratio and the next lower size is the result.

Should the need ever arise for a keyboard that is larger than the conventional keyboard, the DS Standard Ratio™ provides an elegant solution for fitting the larger keyboard into the conventional piano.  The keyboard manufacturer simply reduces the number of natural keys from 52 to 48 and expands the keyboard to fill the available space in the piano. The new larger keyboard that is the next higher size would lose three notes in both the far bass and treble ends of the piano.


   It was interesting to observe that small changes in keyboard size did not make much difference to pianists once they had gotten to a size that was “in their zone.”  For instance, when we built a keyboard with a 6.24 inch octave, a male with an average hand would notice little difference, but a small handed pianist would immediately notice relief.  The exact sizes for the standards were not that critical.
   Although we suggested a keyboard that was larger than the conventional keyboard, no pianist asked to try it.  Given the fact that the large conventional size already exists, we feel confident we are offering nearly optimum sizes for every adult pianist.  All of our observations relating hand span to keyboard size are summed up in the chart below. Notice that the keyboards are divided into overlapping zones, allowing for differences in finger thickness and personal preference.   Although some pianists have purchased custom keyboards, there is no compelling need to have more than these three recommended standards. The forth size in our standard is approprate for a child’s hand.


The hand span data in this chart was collected at the 2004 MTNA National Convention.

There is clarity to the sizes and nomenclature we have chosen.

  • The octave has been defined and a very accurate method for Measuring an Octave has been provided.  Measuring today’s pianos, we find their octaves vary in a small range, from 6.46 to 6.54 inches, and that most manufacturers have gravitated to an octave size that is very close to an even 6.5 inches.  We therefore have established DS6.5® the Conventional Keyboard size.
  • The jumps between our keyboard sizes are comfortable, all having the same ratio of change, the DS Standard Ratio.  The DS6.0® keyboard has an octave that is exactly 6 inches. Since it is the middle size, it is thought of as the Universal Keyboard.
  • A pianist can feel the size of the octave on a DS5.5®   7/8th Keyboard by playing a seventh on a conventional keyboard.
  • Our nomenclature tells you the size of the octave measured in inches or in centimeters from the middle of one C key to the middle of the next C key.

Today the world of the piano has a one-size-fits-all mentality, resulting in profound discrimination and severe medical issues.  If you ask pianists what size keyboard they need, they are confused and do not know because they have spent their life in this one-size-fits-all world.  Our experience in observing pianists respond to a complete range of keyboard sizes has led to this set of standards. This is similar to the idea of offering various sizes in the world of the violin without the disadvantage of having to play a smaller instrument!   Our alternative keyboards fit into all modern pianos.  Regardless of a pianist’s hand size, the Power, Ease, and Artistry available in the modern piano is now within everyone’s Reach. 

Keyboard Size History
Naotaka Sakai measured 75 historical pianofortes found in the collections of the Metropolitan Museum of Art in New York, the Hofburg Collection of Early Musical Instruments in Vienna, the Technisches Museum Wien in Vienna, and the Hamamatsu Museum of Musical Instruments in Hamamatsu, Japan. He published his findings in the Medical Problems of Performing Artists[1]. Converting his data to conform to the Steinbuhler definition of an octave (see Measuring an Octave) and assuming a keyboard of 88 keys to calculate its overall width, we have the following history of piano keyboard sizes.

  • A 1720 Cristofori keyboard was the same size as today’s conventional keyboards:




    or   165mm   octave

    48.25” overall width

  • From 1784 - 1825 keyboards were somewhat smaller, ranging in size from:

    Smallest -



    or   156mm   octave

    45.5”  overall width

    Average -



    or   160mm   octave

    46.8”  overall width

    Largest -



    or   163mm   octave

    47.5”  overall width

  • From 1826 - 1875 keyboards were getting larger and ended in today’s conventional size.
  • From 1876 - 2000 keyboards were the same as today’s conventional keyboards:

    Smallest -



    or   164mm   octave

    48.00”   overall width

     Average -



    or   165mm   octave

    48.25”   overall width

     Largest -



    or   166mm   octave

    48.50”   overall width

  • A notable exception: in the 1920’s & 1930’s Joseph Hoffman performed on a 7/8 keyboard built by Steinway:




    or   144mm     octave

    42”      overall width

  • DS Standard® Keyboards:

    Child’s -



    or   13.0cm  octave

    37.94”   overall width


    7/8th -



    or   14.1cm  octave

    41.10”   overall width


    Universal -



    or   15.2cm  octave

    44.53”   overall width


    Conventional -



    or   16.5cm  octave

    48.25”   overall width


   Note that Mozart, Beethoven, Schubert, Chopin and Schumann would have composed many of their great works on keyboards that were smaller than our present day conventional size.  This makes it doubly understandable why pianists today with small hands will struggle to perform them.
   One reason conventional keyboards are so large is due to the fierce pressure in the 19th century for piano manufacturers to win competitions.  They were driven to produce pianos that had ever bigger sound which meant they would build pianos with more strings and ever bigger hammers. Cristofori’s first keyboards were the same size as in today’s modern pianos, but the initial reaction to his keyboard was to build smaller ones.  Then in the 19th century, as manufacturers strove for market share, designs for the modern piano evolved and extended the width of the keyboard once again.  However, today it is possible to have pianos with very big sound and also to fit them with keyboards that are ergonomically suited to every hand.

1. Naotaka Sakai, MD, PhD: Keyboard Span in Old Musical Instruments, Medical Problems of Performing Artists, December 2008

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