The iOS Keyboard is a very complexe but one of the most important element of the OS. The truth is a lot is known about it but not much is on paper. This page is a attempt to fix that.
Sizes (in pixels)
'''Portait (iPhone, default English US keyboard):'''
Keyboard: 320*216 Keycaps: 15.1*18.8 (approx.)
Space between 2 keycaps: 7.5 (approx.) Space between left edge of screen and Q tile: 7.5 (approx.) Space between shift and Z: 7.5 (approx.) Space between delete and M: 7.5 (approx.) Space from left edge to A: 11.3 (approx.) Space from right edge to L: 11.3 (approx.) Space from top edge to row 1: 7.5 (approx.) Space from bottom edge to last row: 2 (approx.)
Shift: 18.8 *18.8 (approx.) 123: 18.8 *18.8 (approx.) Globe: 18.8 *18.8 (approx.) Dictation: 15.1 *18.8 (approx.) Space Bar: 7.1*18.8 (approx.) Return: 4.1*18.8 (approx.) Delete: 18.8 *18.8 (approx.)
'''Landscape (iPhone, default English US keyboard):'''
Keyboard: 480*162 (3 inch devices) 568*162 (4 inch devices)
Sources:
Personal measurements & http://www.idev101.com/code/User_Interface/keyboard.html