Lens FOV Calculator

Lens FOV: how focal length defines angle of view

A lens's angle of view comes from FOV = 2 · arctan(d / (2·f)), with d as the sensor dimension and f the focal length in mm. Take a full-frame sensor (36 mm horizontal). A 50 mm normal lens covers roughly 39.6°. A 24 mm wide-angle opens up to 73.7°, while a 200 mm telephoto closes down to 10.3°. Smaller sensors bring a crop factor into play — APS-C ≈ 1.5× and MFT = 2× — so a 50 mm on APS-C frames the scene like a 75 mm would on full-frame.

Applications

Pick a wide lens for landscape and architecture, a telephoto for sports and wildlife, or a fisheye for VR 180° immersive capture. It also helps with CCTV planning, when you need to know how much of a hallway or parking lot a given lens actually reaches.

FAQ

Why does a 50 mm look tighter on APS-C than on full-frame? The smaller sensor crops into the image circle, so it grabs a narrower angle even though the focal length hasn't changed.

Which FOV — horizontal, vertical or diagonal? Use horizontal when you care about framing width and vertical for ceiling or sky. Diagonal is the biggest of the three, and it's the figure marketing tends to quote.

Does the formula work for fisheye lenses? Roughly, at best. Fisheyes rely on non-rectilinear projections, which means 2·arctan comes in under the real FOV.