Optical magnification calculator
Enter the object height and the image height (negative if inverted) to get the magnification. Add the object distance and it also gives the image distance.
Loading the tool…
Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Enter object height, image height (negative if inverted) and object distance (optional).
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
m = hᵢ / hₒ = −dᵢ / dₒ, so the image distance is dᵢ = −m × dₒ.
Example
Inputs: Object height = 2 cm, Image height (negative if inverted) = -6 cm, Object distance (optional) = 10 cm. Result: Magnification: -3 ×; Orientation: Inverted; Size: Enlarged.
Limits and caveats
- This is linear image magnification. Magnifiers and telescopes are usually rated by angular magnification, which is a different calculation.
Questions about this tool
What does a magnification of −3 mean?
The image is three times larger than the object and upside down.
Does magnification have a unit?
No. It is a ratio of two lengths in the same unit, usually written with ×.
Why is the image distance positive with a negative magnification?
An inverted image from a converging lens is real and forms on the far side, which means a positive distance.