Lens / Mirror

This tool uses the Cartesian convention 1/f = 1/dₒ + 1/dᵢ. Positive f describes a converging lens or concave mirror. Positive dₒ is a real object on the incoming side; positive dᵢ is a real image (on the other side for a lens and on the object side for a mirror).

Select the quantity to solve for. The diagram is schematic: it distinguishes real and virtual images but does not use a physical scale.