Thin Lens Equation Calculator
Locate the image formed by a converging or diverging lens.
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Thin Lens Equation Calculator by TheCalcTools
How the Thin Lens Equation Calculator works
Enter the focal length (positive for a converging lens, negative for diverging) and the object distance.
The thin lens equation gives the image distance.
A positive image distance is a real image on the far side; negative means a virtual image.
The formula
Worked example
Using the default values shown in the calculator:
| Focal length (cm) | 10 |
|---|---|
| Object distance (cm) | 25 |
- 1 ÷ dᵢ = 1 ÷ 10 − 1 ÷ 25.
- dᵢ = 16.67 cm, magnification = -0.67.
- The image is Real, inverted.
Result:
| Image distance (cm) | 16.667 |
|---|---|
| Magnification | -0.667 |
| Image | Real, inverted |
| Lens power (dioptres) | 10.00 |
Frequently asked questions
What is a real vs a virtual image?
A real image is formed where light rays actually meet and can be projected on a screen. A virtual image cannot be projected, as with a magnifying glass.
How do I use it for a camera?
Photography lenses form a real inverted image on the sensor. Focus adjusts the object-to-image distance.
Sources and further reading
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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.