This Piano Technician's Calculator has the standard equations and constants used in piano tuning based on methodology found in The Calculating Technician by David Roberts, published by The Piano Technicians Guild Foundation Press.     

Uses

Technicians use these formulas on a regular basis.  Inharmonicity is interesting and a good technician will attempt to make the graph of this formula move as smoothly as possible as it progresses up the keys, taking special notice when the strings change from single strands to wrapped.  

   (images courtesy of Wikipedia) 

Thanks

Special thanks to my friends Austin Abrahams and Ted Black for pointing me to the math used in this trade.