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Lens and Mirror Calculator
Find image distance, focal length or magnification for a thin lens or mirror from the object distance in front of it using the lens equation.
1 ÷ f = 1 ÷ d_obj + 1 ÷ d_img
For a thin lens or mirror the reciprocals of focal length, object distance and image distance add up, and a negative result means a virtual image.
Image distance
— cm
The calculation runs entirely in your browser — no data leaves your device. Change any number and the answer updates instantly.