So, I took a straight edge along my backside, and measured from there to the tip of my knee...
Seat Pitch on a plane measures between the same places in seats, so back to back, not "the free space between seats."
On the back part of an AA MD80, the seat pitch is 31", and the seat is just about 5" thick.
In other words, I'm mashing myself into those seats.
BEFORE YOU LEAN BACK IN YOUR CHAIR, AND THEN SLAM INTO IT WHEN IT STOPS MOVING EARLY, CHECK TO SEE IF YOU ARE INJURING THE PERSON BEHIND YOU! YOU ARE NOT ENTITLED TO INJURE SOMEONE JUST BECAUSE YOUR SEAT HAS A RECLINE OPTION!!!
But really, I was measuring this to see what sorts of GA planes I could fit into.
Seat Height: My lower leg needs 25" to clear the yoke,
Leg Room: My upper leg needs 27" to clear the panel or seat in front of me.
Seat Pitch: 27" plus the thickness of the seat.
Seat Width: 19" if my pockets are empty.
Headroom: My torso needs 39" from the seat to the top of the cabin.
Obviously, some angles can be factored in here, but if my lower legs have to bend back, then it limits my ability to operate the rudder.