Focal Length Calculator
Calculate the required focal length to achieve a specific field of view. Enter your sensor size and desired angle of view to find the ideal lens focal length.
Horizontal field of view angle
How to Use This Calculator
- Select your camera\'s sensor type from the dropdown, or choose "Custom" to enter specific sensor width.
- Enter your desired field of view in degrees (horizontal angle of view you want to capture).
- The calculator displays the required focal length in millimeters to achieve that field of view.
- Use this information to choose the right lens or understand how your current lenses will perform.
Focal Length Formula
Focal length is calculated from sensor width and desired field of view:
Example: For a 50° field of view on a full-frame sensor (36mm wide): Focal Length = 36 ÷ (2 × tan(25°)) = 38.6mm. This is why 35-40mm lenses are considered "normal" on full-frame cameras.
Full Description
Choosing the right focal length is crucial for achieving your desired composition. This calculator helps you work backwards from your vision: if you know what field of view you want, it tells you exactly what focal length lens you need. This is especially useful when planning lens purchases or understanding how different lenses will frame your shots.
The relationship between focal length, sensor size, and field of view is fundamental to photography. Longer focal lengths narrow the field of view (telephoto effect), while shorter focal lengths widen it (wide-angle effect). Sensor size also plays a crucial role—smaller sensors effectively "crop" the image, requiring shorter focal lengths to achieve the same field of view as larger sensors.
Use this calculator to plan your shots, choose lenses, and understand how your camera system compares to others. Whether you\'re shooting landscapes, portraits, or anything in between, knowing the right focal length helps you capture exactly what you envision.
Frequently Asked Questions
How do I find my sensor size?
Check your camera's specifications or manual. Common sensor sizes: Full-frame (36×24mm), APS-C Canon (22.3×14.9mm), APS-C Nikon/Sony (23.5×15.6mm), Micro Four Thirds (17.3×13mm). The calculator includes presets for these common formats.
What field of view should I use?
Field of view depends on your shooting needs: Wide angle (50°+) for landscapes, normal (40-50°) for general photography, telephoto (<30°) for portraits and wildlife. Human vision is approximately 50° horizontally.
Can I use this to choose a lens?
Yes! Enter your desired field of view and sensor size, and the calculator will tell you what focal length lens you need. This helps when planning purchases or choosing from your lens collection.
How does sensor size affect focal length?
Smaller sensors require shorter focal lengths to achieve the same field of view. A 24mm lens on APS-C gives similar FOV to 36mm on full-frame. This calculator accounts for sensor size automatically.