Practical tools for measured work
Thin lens calculator
Calculate real or virtual image position, magnification and signed image height.
Calculate the layout, check the diagram, then print the result for the shop or jobsite.
How it works
1/f = 1/object distance + 1/image distance. Magnification is minus image distance divided by object distance. Positive focal length represents a converging lens. Positive image distance is a real image on the opposite side; negative image distance is virtual. Negative magnification means inverted.
Current-input example
The result above uses these exact values. This snapshot is included when the page is printed so the output can be checked against the original measurements.
- Signed focal length
- 10 cm
- Real object distance
- 30 cm
- Object height
- 2 cm
Primary result: Image distance: 15 cm.
Before using the result
- Check the selected mode, units and input values before using the result.
- Read the assumptions and rounding rules; compare the worked example with your intended calculation.
- A numerical result does not supply missing context or change the stated limitations.
Limitations
Paraxial thin-lens approximation for a real object in air. It excludes lens thickness, aberrations, multiple lenses and optical safety assessments. Distances use the same centimetre unit.
Frequently asked questions
What should I verify before using this result?
Check the input values, units, dates and assumptions. Compare the method and its stated limits with the source relevant to your task.
Why might the finished result differ?
Results depend on the entered data and the model’s assumptions. Rounding, changing conditions or omitted factors can affect the comparison. Read the limitations before using the result.
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