Partometer - your camera tape measure. Calibrate once, measure as many as you want.

Once calibrated using known object, Partometer App   allows you to do multiple measurements in the plane. Measurement plane has to be parallel to the camera. Measurement results can be shown in different units along with relative (to a reference) values. It helps to divide the object in certain ratio. If an object doesn’t fit into camera view you can take a picture from a side and use Partometer3D App that extends functionality of Partometer to any defined plane in 3D.