calculating video size

Hello,

I'm trying to render 1 input video to multiple videos in X columns and Y rows on the screen. I tried to use videoplane and calculate position and size (scale) for each output clip.

I want to be able to specify how many clips I want (num of rows and columns) and output multiplicated clips on the window. The problem I have is that I don't know how I should calculate clip positions and sizes based on the original size.

Does anyone know how to calculate the position and scale for each clip? I know that position should be between -1 and 1, but it depends on a video scaling and original video size (I think?). How to incorporate that data, even though the video is not square size?

Thanks for help,

Here's my current attempt: