Macro Magnification Calculator
Fill in the values and the answer updates as you type.
How the Macro Magnification Calculator 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.
Inputs and results
The Macro Magnification Calculator takes 3 inputs and gives 4 results.
What you enter
- Sensor height (mm) — starts at 24.
- Subject height filling the frame (mm) — starts at 60.
- Lens aperture (f-number) (f/) — starts at 2.8.
What you get
- Magnification (×)
- Reproduction ratio
- Effective aperture (f-number)
- Exposure loss (stops)
Example: Macro Magnification Calculator with the starting values
With sensor height 24 mm, subject height filling the frame 60 mm and lens aperture (f-number) 2.8 f/, the calculator returns:
| Magnification (×) | 0.4 |
|---|---|
| Reproduction ratio | 1:2.5 |
| Effective aperture (f-number) | 3.9 |
| Exposure loss (stops) | 1 |
Change any value above and the results update straight away.
Macro Magnification Calculator FAQ
How do I use the Macro Magnification Calculator?
Enter sensor height, subject height filling the frame and lens aperture (f-number) in the fields, then read magnification (×), reproduction ratio, effective aperture (f-number) and exposure loss (stops) in the result panel. The answer updates as you type, and you can press Calculate or Enter to refresh it. Use “Copy link” to share your exact numbers with someone else.
What does the Macro Magnification Calculator calculate?
Reproduction ratio, effective aperture, and exposure loss for close-ups. It returns magnification (×), reproduction ratio, effective aperture (f-number) and exposure loss (stops) from the 3 values you provide.
What values does the Macro Magnification Calculator start with?
It opens with sensor height 24 mm, subject height filling the frame 60 mm and lens aperture (f-number) 2.8 f/ so you can see a working result straight away. Replace them with your own numbers, or press Reset to return to these starting values.
Is the Macro Magnification Calculator free and private?
Yes. It is free, needs no account, and runs in your browser, so nothing you type is sent to or stored on our servers. See the Privacy Policy for details.
Can I rely on the Macro Magnification Calculator for important decisions?
Treat the result as a well-rounded estimate. Real situations often have details a general calculator cannot know, so confirm important decisions with a qualified professional. See the Disclaimer for more.