Thin Lens Equation Calculator
Solve focal length, object distance or image distance and inspect signed lateral magnification.
What would you like to do next?
Solve one unknown in the thin-lens relationship
Select focal length, object distance or image distance as the unknown, then enter the other two values in centimeters. The calculator returns the completed distance set and signed lateral magnification. Keeping units and signs visible helps students and bench users distinguish real and virtual configurations instead of treating every distance as an unsigned length.
Choose and preserve one sign convention
Optics texts can present equivalent equations with different sign rules. This page expects one internally consistent thin-lens convention and does not infer how a physical setup was labeled. Thick lenses, multiple elements, principal-plane offsets and aberrations require ray tracing or measured calibration. Verify the image orientation and location before using a computed value in an instrument.
Frequently asked questions
Can a lens distance be negative?
Yes. A consistent sign convention uses negative values for some virtual configurations.
What does negative magnification indicate?
Under the stated convention it indicates an inverted image.
Does the page model lens thickness?
No. It uses the thin-lens approximation.