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Lens Formula Calculator

Thin lens equation (1/f = 1/v − 1/u): solve for focal length, object or image distance, with magnification.

Enter values

Results update as you type.

Result

Image distance

15 cm

Magnification
-0.5 ×
Image type
Real and inverted
Size
Reduced

About the Lens Formula Calculator

Thin lens equation (1/f = 1/v − 1/u): solve for focal length, object or image distance, with magnification.

Also known as: thin lens equation, image distance calculator, object distance, lens equation, image-distance, object-distance.

How to use this calculator

  1. Enter solve for.
  2. The result updates instantly as you type — press Calculate (or Enter) at any time.
  3. Review the breakdown shown under the main result.
  4. Use Copy result or Share to save the answer or send a link with your inputs.

Formula

1/f = 1/v + 1/u · m = −v/u

Worked example

Using the values pre-filled in the calculator above:

  • Solve for: Image distance
  • Focal length = 10 cm
  • Object distance = 30 cm

the calculator returns:

  • Image distance: 15 cm
  • Magnification: -0.5 ×
  • Image type: Real and inverted
  • Size: Reduced