f-stop to Aperture Area Converter
Enter an f-number and focal length to find the aperture diameter and area.
Result
How to use
- Enter your values in the fields above.
- Press Calculate to see your result instantly.
- Use the Share button to copy a link to your result.
About this calculator
Relative aperture area follows area ∝ 1/N², where N is the f-number, which is why each full stop (f/2.8 to f/4, for example) halves the light-gathering area. With focal length known, the physical aperture diameter is d = focal length / N, and the physical area is π × (d/2)².
Photographers and optical engineers use this to see the actual size of the lens opening behind an abstract f-number, to sanity-check a lens's maximum aperture against its stated specs, or to compare how much physical glass and light-gathering area two lenses with different focal lengths need to reach the same f-stop.
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