A method and arrangement for calibrating stereo cameras. A first image from a first camera is received, and a second image is received from a second camera, the first image and the second image comprise an overlap. One or more candidate points of the first image and of the second image are determined in the overlap. The candidate points of the first image are matched with the candidate points of the second image and pairs of corresponding candidate points are determined. A homography of the first camera is calculated based on the pairs of corresponding candidate points and a homography of the second camera is calculated based on the pairs of corresponding candidate points. The first camera and the second camera are calibrated by adjusting an intrinsic parameter or an extrinsic parameter of each respective camera, based on the calculated homography of each respective camera.