Field of View Calculator
Calculate the horizontal coverage width (and height) at a given subject distance for any lens, sensor, and crop factor combination. Perfect for planning surveillance setups, portrait framing, or landscape compositions.
Last updated: May 2026
About this calculator
Field of view (FOV) is the real-world area visible through a lens at a given distance. The horizontal coverage width is: FOV_width = 2 × distance × tan(arctan(sensorWidth / (2 × focalLength × cropFactor))). Here, sensorWidth / (2 × focalLength × cropFactor) is the half-angle tangent of the lens on the effective (cropped) focal length. Multiplying by 2 × distance converts that half-angle into a full width at the subject plane. The crop factor accounts for sensors smaller than the full-frame 35 mm standard — a crop factor of 1.5 on an APS-C body makes a 50 mm lens behave like a 75 mm lens in terms of field of view. Vertical FOV is computed identically using sensorHeight in place of sensorWidth. This formula assumes a rectilinear (non-fisheye) lens and a flat subject plane perpendicular to the optical axis.
How to use
You have a 50 mm lens on a full-frame camera (sensorWidth = 36 mm, cropFactor = 1) shooting a group portrait at 3 m distance. FOV_width = 2 × 3 × tan(arctan(36 / (2 × 50 × 1))) = 6 × tan(arctan(0.36)) = 6 × 0.36 = 2.16 m. So your frame captures roughly 2.16 m of width at 3 m — enough for about 5–6 people standing shoulder to shoulder. If you switch to an APS-C body (cropFactor = 1.5), the same lens gives FOV_width = 6 × tan(arctan(36 / (2 × 50 × 1.5))) = 6 × tan(arctan(0.24)) ≈ 6 × 0.235 = 1.41 m, noticeably tighter.
Frequently asked questions
How does focal length affect the field of view of a camera lens?
Shorter focal lengths produce a wider field of view, while longer focal lengths narrow it. This is because a shorter focal length bends light more sharply, capturing a larger angle of the scene onto the same sensor. For instance, a 24 mm wide-angle lens might capture 74° horizontally on a full-frame sensor, while a 200 mm telephoto lens captures just about 10°. Changing focal length is the primary way photographers control how much of a scene fits in the frame from a fixed position.
What is crop factor and how does it change the effective field of view?
Crop factor describes how much smaller a camera's sensor is compared with a 35 mm full-frame sensor (36 × 24 mm). A common APS-C sensor has a crop factor of 1.5–1.6×, meaning the sensor captures only the central portion of the image circle a lens projects. This effectively multiplies the lens's focal length equivalently — a 35 mm lens on a 1.5× crop body behaves like a 52.5 mm lens on full frame in terms of field of view. For telephoto reach this is beneficial, but it can be limiting for wide-angle work.
How do I calculate how wide an area my security camera covers at a given distance?
Use the field of view formula: coverage width = 2 × distance × tan(arctan(sensorWidth / (2 × focalLength × cropFactor))). You need the camera's sensor width (often 1/3" or 1/2.7" chips with ~4–6 mm width), the lens focal length (typically 2.8–8 mm for security cameras), and the monitoring distance. For example, a 2.8 mm lens on a 1/3" sensor (sensorWidth ≈ 4.8 mm, cropFactor ≈ 1) at 5 m gives coverage of about 2 × 5 × tan(arctan(4.8/5.6)) ≈ 8.6 m wide. This helps you determine how many cameras are needed to cover a given area without blind spots.