Lens Magnification Calculator
Estimate macro reproduction ratio from focal length and subject distance.
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Introduction
Lens Magnification Calculator — Estimate macro reproduction ratio from focal length and subject distance. Enter Focal Length, Subject Distance to get an instant, accurate result.
Formula
Thin-lens magnification m = f / (d − f), where f is focal length and d is subject distance (same units, e.g. mm).
Step-by-step
- Enter the Focal Length.
- Enter the Subject Distance.
- Click Calculate to see your result instantly.
Real-world example
Example: With Focal Length = 100 mm, Subject Distance = 200 mm, the Lens Magnification Calculator gives a result of 1.
Frequently Asked Questions
What does a magnification of 1.0 mean?
The subject is projected onto the sensor at true life size (1:1) — the definition used for macro lenses.
What happens if subject distance equals focal length?
The formula is undefined at that point (division by zero), since the subject would be at the lens's focal point rather than forming a real image.
What inputs does the Lens Magnification Calculator need?
You'll need to provide: Focal Length, Subject Distance. All fields use sensible defaults, so you can see a working example immediately and then adjust the values to match your own numbers.
How accurate is the Lens Magnification Calculator?
The Lens Magnification Calculator applies the formula exactly as calculated — Thin-lens magnification m = f / (d − f), where f is focal length and d is subject distance (same units, e.g. mm). — so results are precise for the inputs you provide. Accuracy depends on entering correct, realistic input values.
Is the Lens Magnification Calculator free to use?
Yes, the Lens Magnification Calculator is completely free, requires no signup, and runs instantly in your browser.
About the Lens Magnification Calculator
The Lens Magnification Calculator uses a real, verifiable formula — Thin-lens magnification m = f / (d − f), where f is focal length and d is subject distance (same units, e.g. mm). — so results are accurate every time, not an approximation.