What it's for
Field of view (FoV) measures how much of a scene a lens frames, in degrees. This calculator gives you the horizontal, vertical and diagonal angle based on focal length and sensor format, and, if you provide the subject distance, also calculates the actual width and height of the captured frame.
Formulas used
The angle of view on each axis is angle = 2 · atan(sensor_dimension / (2 · f)), where the sensor dimension is width, height or diagonal (found via Pythagoras: diagonal = √(width² + height²)), and f is the focal length in the same unit. When subject distance is given, frame size is frame_width = 2 · distance · tan(horizontal_angle / 2) (and the same for height).
Sensor dimensions used
We use the approximate physical dimensions (width × height, in mm) of each format: Full Frame 36×24; APS-C Canon 22.3×14.9; APS-C Nikon/Sony 23.5×15.6; Micro 4/3 17.3×13; 1-inch 13.2×8.8; smartphone (~1/2.3") 6.17×4.55 — standard industry values for each format.
Worked example
A 24mm lens on a full-frame camera has a horizontal field of view of about 74°, typical of a wide-angle lens used for landscape and architecture photography.
Limitations
The calculation assumes a rectilinear lens with no significant distortion — fisheye or heavily barrel-distorted lenses don't follow this formula exactly. Smartphone sensor dimensions vary a fair amount between models; the value used here is only a reference.
Frequently asked questions
What's the difference between horizontal, vertical and diagonal angle?
Horizontal and vertical measure the field captured along the sensor's width and height respectively. Diagonal measures corner to corner — it's usually the value quoted as a lens's "angle of view" in manufacturer specs.
Why does the same focal length frame differently on different sensors?
Because the field of view depends on the relationship between focal length and the sensor's physical size. Smaller sensors capture a narrower angle with the same lens — that's the crop factor effect, calculated in our crop factor calculator.
What's the point of calculating frame size at a distance?
It's useful for planning shots — for example, knowing how many meters wide a lens will capture at 10 meters away, useful for product photography, portraits or video.