The calculation is simple when you know the space group and lattice parameters. You could try the program Chekcell, for instance, to do it. It is available at www.ccp14.ac.uk
Use a standard XRD peaks pattern of perovskite structure. It will includes the hkl values and the corresponding positions and relative intensities of the peak.
It is very easy because perovskite is either cubic or tetragonal. you just measure the angle of diffraction for each reflection ,then use Bragg s law to get the inter-planer spacing then use any x-ray powder program to index the pattern and get hkl for each XRD reflection.
You can use the POWDERX software to calculate d-spacing, lattice parameters etc . other way , you can pick the 2 theta value for each peak and use Bragg's Law to calculate d- spacing.
In this video tutorial, I have explained in detail the d-spacing (interplanar spacing) and how to calculate it from the XRD data using OriginLab software. In the case you want to further ask about it, please do comment on the specific video, I'll respond to it shortly. I have provided the practice as well as calculations files here. Thanks