This thread is absolutely ridiculous. To answer the OP's question, if the length of each square is 1 inch, the length of the diagonal is sqrt(2) inches.
You're missing the point. It doesn't matter if a sqaure is a square inch or a square mile, A King moving can only move 1 square! The smallest unit of length on a chessboard is one square, regardless of what it actually measures!
It's you who's missing the point, ErrantDeeds.
The hypotenuse only looks equal to the catheti on the chessboard just because the diagonals it's made of are longer than the sides of the squares that the catheti are made of.
In other words, your "unit" of one square is diagonally longer than it is horizontally or vertically. It's not constant.
Try and draw a right rectangle with equal catheti on a beach. Now walk along a cathetus keeping constant pace length. Note the number of steps. Now walk along the hypotenuse.
Not surprisingly, you too - like the king on a chessboard - can walk along the hypotenuse in the same number of steps as you did along the cathetus, as long as you take longer steps (i.e.: you change your unit's length when walking diagonally).
what in the world are you all arguing about. the original question is a brain-fart of a postulate thats gone way to far!
We're just having a bit of fun buddy.