Thin Lens Equation Calculator

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Calculates the focal length, object distance, or image distance for a thin lens using the thin lens equation: 1/f = 1/do + 1/di.

How To Use

How to use this calculator

Start with your values, or try a preset.

Step 1

Enter Object Distance (do) and Image Distance (di) in the units shown.

Step 2

Read Focal Length (f) in the results panel. Results update as you change the inputs.

Step 3

Choose a preset to load an example, then adjust the values for your situation.

Worked Examples

See the inputs and their calculated results.

Object Distance (do): 20 cm; Image Distance (di): 40 cm

Focal Length (f): 13.33333333 cm

Object Distance (do): 10 cm; Image Distance (di): 10 cm

Focal Length (f): 5 cm

Object Distance (do): 30 cm; Image Distance (di): 60 cm

Focal Length (f): 20 cm

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