The large professional level of piano measures 50″ and taller (above 125cm). These are the ‘grandiose’ versions of professional upright pianos. True, an actual grand piano has a different action than any upright piano but when it comes to string length, large upright pianos have strings equivalent to medium sized grand (See the string length chart in the article What Size Piano Should I Buy?) Traditionally, most 100 year old pianos were 55″ tall (137cm) and it’s only been in more recent decades that makers have made smaller pianos. A 48″ tall piano (121cm) will deliver what is necessary for advanced level playing but 52″ (132cm) pianos are pure luxury. Today, the tallest pianos in production range 50-52″ tall (125-132cm) but there is a movement to the taller pianos from yesteryear that measure closer to 140cm or 55″ in height. See our article entitled Emerging Giants in the Piano Industry
For more information on piano sizes, please refer to the Piano Price Point article What Size Piano Should I Buy?