Question: how to calculate hkl values from xrd?
Answer: A. ... 
Recognize the hkl values for the first few peaks: 100, 110, 111, 200, 210, 211, 220, etc.
Calculate the interplanar spacing, d, for each peak:
1/d2 = (h2 + k2 + l2)/a2. ... 
Use Bragg's Law to determine the 2θ value: λ = 2d.