I need to know for a project that I'm doing
A Kawai studio model acoustic piano vintage 1980 or so that I have access to where I work has the following key dimensions (visible portion only, if you need the hidden part, which is much larger, let me know):
White key width = exactly 7/8 inch. Visible length = 6 in., including a 1/16" "lip" on the top surface that sticks out beyond the end of the key proper. Visible height when not depressed = 7/8 in.
Black key width at white key level = 15/32" tapering up to 7/16" at the top, which is 1/4 in. above white key level. Length at white key level 3 15/16" tapering back to 3 5/8" at the top.
Horizontally across the width of the keyboard there is approximately 1/16" gap between keys.
When I get home tonight I'll measure my Panasonic 88-note electronic and see if it differs. (For one thing I know it does not have the 'lip' on the white keys.) If it is substantially different from the above I'll post a comment to this answer.
EDIT: Well, I was wrong about the lip on the white keys. My electronic piano has them too! I had never noticed that. The white keys are exactly 1/8 in. shorter in length than on the acoustic, but otherwise identical. The black keys are 1/16 in. wider and 3/16 in. taller, but otherwise identical. So all in all the two pianos are so extremely similar as to be almost identical. Certainly the 88 note keybed (where the notes are placed) is within 1/8" of being exactly the same length. I have no idea what you needed all this for, but have fun with it!