scores and pesky fingering limits

[trampofnine]

Is there any plug in, book or anything that gives a guideline for when an interval is too wide for the pianist [in my case of piano composing], or in other instruments, to be able to play physically? Or is such a question pointless when people have different sized fingers anyway and anything can be played even if modification [e.g bringing notes down a few octaves] is needed?

[MadBrain]

For piano, essentially everyone can play an octave on one hand, but probably 95%+ of people can't easily play a 10th (at least, not without rolling it, not fast, not easily, not if there are any black keys involved, not reliably and not without some extreme stretching... on accordion it is possible though, due to the small size of the keyboard).

Some people do have freakishly large hands though

This site has more info:
http://www.thesmallhandedpianist.com/

[Nightpolymath]

It is not unknown for composers such as Beethoven and Brahms to spite so called piano virtuosos of the day by writing sonatas & concertos that are seemingly impossible to play.