Here is a nice tutorial for those who work with crystal structures.

http://www.youtube.com/watch?v=jt7qlWTBZqUto calculate d-spacing in excel from 2-theta,

type in excel

=A1/(2*SIN(RADIANS(A2/2)))

where in A1, there should be x-ray wavelength.

A2, is the 2-theta value.