Macro Magnification Calculator
Reproduction ratio, effective aperture, and exposure loss for close-ups.
How it works
Magnification = sensor size ÷ subject size. At close range the lens extends, so the effective aperture is N × (1 + m), and the light loss in stops is 2 × log2(1 + m). A true macro lens reaches 1:1, meaning the subject appears life size on the sensor. Most cameras meter through the lens and correct exposure for this automatically, but flash and handheld meters do not. Example: Filling a 24 mm frame height with a 60 mm subject gives 0.4× magnification (1:2.5), and f/2.8 behaves like f/3.9.
FAQ
Is this calculator free?
Yes. No signup is needed and nothing you enter is stored.
Is the result exact?
Results are rounded for display. For financial, medical, or legal decisions, confirm with a professional.
Do my numbers leave my device?
No. The calculation runs in your browser.