๐Lens Equation Calculator
Enter any two of focal length, object distance, and image distance to solve for the third.
Sign convention: converging lens f > 0, diverging lens f < 0. Leave one field blank to solve for it.
Free Lens Equation Calculator
This lens equation calculator solves the thin lens formula 1/f = 1/dโ + 1/dแตข for whichever variable โ focal length, object distance, or image distance โ you leave blank. It also computes magnification (m = โdแตข/dโ) and tells you whether the resulting image is real or virtual, and upright or inverted.
Using the standard sign convention: a converging (convex) lens has positive focal length, a diverging (concave) lens has negative focal length, positive image distance means a real image on the opposite side, and negative image distance means a virtual image on the same side as the object.
Useful for optics coursework covering lenses, cameras, and the eye. Free, runs entirely in your browser, no sign-up required.