Orthographic camera size for 1080p quad @ 1920mx1080m

How do you calculate the orthographic camera size for a 1080p quad?

the height of the camera is twice the camera.ortographicsize. so the ortographic size for matching height should be 540. for getting the 1920 resolution your device must be having the desired aspect ratio, 16:9, mathcing the height with a 16.9 aspect ratio will give you the 1920x1080