How far can your hand stretch on the piano?

A tenth on the white keys. A minor tenth I can do ex. C-E flat, but major tenth like E-G# I can do. And all this is easier for my left hand and takes slightly more effort in the right. I have flexible hands from practicing special exercises and never locking the wrists, but short 5th fingers. I wouldn't mind having an extra one or two centimeters of reach, but I can't fight the limitation mother nature bestowed on me.

An octave playing mostly on the edge of the keys, and occasional 9th using the side of the keys to assist the stretch.

I can "just" manage a 9th in each hand, but only an octave comfortably! It's a good job I tend to prefer the more "intricate" pieces in the repertoire! :)

I can reach a 10th in both hands at a stretch (slightly uncomfortable and thumbs on front edge of key). A 9th is more comfortable to play in both hands

 Between two black notes, a tenth (but I cannot do much with the fingers in between). 

Between two white notes, safely, a ninth; if the thumb is taking two adjacent notes (a la Beethoven), a tenth, but again the fingers in between cannot reach very much. 

I can reach an octave relatively comfortably with both hands. I'm happy with that! Thurmond can reach an 11th in both hands, and his "goal" is to reach a 12th (he still has a few years of growing, so it is possible!). 

Playing final chord of Chopin' Harp Etude and Liszt' Liebestaum III, I use RH for top three notes (Eb3-C4-Ab4) and LH for Ab2-Ab3 (Harp) and Ab3(Lieb). Same voicing with one less note from Liszt...who'd have guessed!

Nine notes comfortably and ten most times. I’m comfortable with playing octaves using 3rd, 4th or 5th finger. Feels like a survey.

I can comfortably play any kind of 10th all day, but I can just barely stretch to an 11th on the white keys.