Camera FOV Calculator — Lens Field of View, Focal Length and CCTV Lens

Work out a lens’s field of view from focal length and sensor size

This camera FOV calculator tells you how much of a scene a lens takes in. Choose your sensor size, enter the focal length and the distance to your subject, and it gives the horizontal, vertical and diagonal angle of view, the width and height of the area in frame at that distance, the 35 mm-equivalent focal length and the crop factor, with a top-view drawing.

Two extra calculators sit underneath. The CCTV lens calculator works backwards from the area a security camera must cover to the focal length it needs, suggests the nearest common lens sizes and checks pixel density against the detect, observe, recognise and identify tiers. The focal length calculator from an image estimates the focal length of a photo from an object of known size.

Everything is plain geometry computed in your browser — nothing is sent anywhere. Photographers, filmmakers, drone pilots, security installers and architects planning camera positions can all use it.

How to use the camera FOV calculator

1. Pick your sensor size from the list, or type the exact width and height from your camera’s specification sheet.
2. Enter the focal length marked on the lens (for a zoom, the setting you will use) and the subject distance in metres or feet.
3. Read the angle of view and the scene size. Tick Close-up for macro and portrait distances, where focusing narrows the view.
4. For a security camera, type the scene width you need covered and the camera’s horizontal resolution to get the lens size and pixel density.
5. To identify the lens used for a photo, measure an object of known width in pixels and enter it in Focal length from a photo.

Camera FOV Calculator features

The field of view formula

A lens focused at infinity projects the scene onto the sensor from a point one focal length away. The angle of view across a sensor dimension d is therefore AOV = 2 × atan(d ÷ 2f), and the width covered at distance D is 2 × D × tan(AOV ÷ 2), which simplifies to D × d ÷ f. Example: an APS-C sensor 23.5 mm wide with a 35 mm lens gives 2 × atan(23.5 ÷ 70) = 37.1° and covers 6.71 m at 10 m.

The same formula with the sensor height gives the vertical angle, and with the diagonal √(w² + h²) gives the diagonal angle — the figure lens makers usually print. A 50 mm lens on full frame (36 × 24 mm) covers 39.6° horizontally, 27.0° vertically and 46.8° diagonally.

When you focus close, the lens moves away from the sensor and the view narrows. With Close-up ticked the calculator uses the thin-lens image distance v = f × u ÷ (u − f) in place of f. Real lenses, especially internal-focus zooms, can differ from this (focus breathing), so treat close-up figures as estimates.

Sensor sizes and crop factor

Crop factor is the full-frame diagonal (43.27 mm) divided by your sensor’s diagonal. Multiply a focal length by it to get the 35 mm-equivalent focal length that gives the same angle of view on full frame. Sizes below are typical values from the Wikipedia “Image sensor format” table, checked against makers’ specification pages (for example Fujifilm GFX100 II 43.8 × 32.9 mm and Canon EOS R7 22.3 × 14.8 mm) on 24 October 2026. Models differ slightly, so type your camera’s exact figures if you know them.

Inch names such as 1/2.3″ or 1/3″ are not measurements: they come from the old video camera tubes, and a “1-inch” sensor is only 15.9 mm across its diagonal.

Choosing a CCTV lens

Security cameras are specified by the area they must cover. The calculator divides sensor width × distance by the required scene width to find the focal length, then lists the nearest common fixed lenses (2.8, 3.6, 4, 6, 8, 12, 16, 25, 35, 50 mm). Picking the shorter one keeps the whole area in view; picking the longer one gives more detail.

Pixel density is the camera’s horizontal pixels divided by the scene width in metres. IEC EN 62676-4 uses it for the DORI tiers: 25 px/m to detect a person, 63 to observe, 125 to recognise a known person and 250 to identify a stranger (figures from an Axis Communications white paper on the standard). Real results also depend on light, compression and focus.