# given four points to calculate the size of the area

I use Calib3d.findHomography with RANSAC to get four points of the detected area and I can draw the bounding box. Here is the question: given these four points, how can I calculate the size of the area? Any functions and code to use? Thanks a lot!

I think you need Shoelace formula

contourArea() ?

ooops! I forgot contourArea()