F-Number Calculator
Calculate f-number (f-stop) from focal length and aperture diameter
About this calculator
The F-Number Calculator helps photographers and optics professionals determine the f-stop value by calculating the ratio between focal length and aperture diameter. This fundamental photography tool is essential for understanding exposure settings, depth of field control, and lens specifications. Whether you're working with camera lenses, telescopes, or other optical instruments, this calculator provides accurate f-number calculations to optimize your optical setup and achieve desired photographic results.
How to use
Enter your lens focal length in millimeters and the aperture diameter in millimeters into the respective input fields. The calculator will instantly compute the f-number by dividing focal length by aperture diameter. The result shows your f-stop value, helping you understand your lens's light-gathering capability and depth of field characteristics.
Frequently asked questions
What is an f-number in photography?
The f-number (f-stop) represents the ratio of lens focal length to aperture diameter, controlling how much light enters the camera and affecting depth of field.
How does f-number affect my photos?
Lower f-numbers (wider apertures) create shallow depth of field and allow more light, while higher f-numbers provide greater depth of field with less light.
Why calculate f-number manually?
Manual calculation helps understand lens characteristics, verify specifications, design custom optics, or work with non-standard lenses and optical equipment.