CCTV Field of View Calculator — FOV Angles, DORI Zones & Pixel Density

How to Use the CCTV FOV Calculator

Select your camera's sensor format and resolution from the dropdowns on the left, then adjust the focal length using the slider or type a value directly into the input field. The calculator updates all results in real time — horizontal and vertical FOV angles, coverage width and height at your chosen target distance, pixel density in pixels per metre, and the corresponding DORI classification.

Use the Mounting Height and Tilt Angle sliders to configure the side-view elevation diagram. This shows you the camera's vertical coverage cone and the size of the blind spot directly beneath the mounting point — a common oversight on wall and pole installations.

The Target Distance slider lets you probe any point along the camera axis. Move it closer to see how pixel density improves; move it further to find the DORI limit for your specific camera and lens combination.

Understanding DORI Zones in Security Camera Design

DORI is a standard defined in EN 62676-4 that classifies what a camera can realistically be used for at a given distance, based on pixel density in pixels per metre (px/m). The four zones are:

• Detect (25 px/m) — sufficient to determine that a person or vehicle is present in the scene. Suitable for perimeter monitoring and wide-area detection.
• Observe (62 px/m) — enough detail to describe clothing, general appearance, or direction of travel. Used for monitoring crowd movement or access points.
• Recognise (125 px/m) — allows identification of a previously known individual with reasonable confidence. Relevant for entrance and lobby coverage.
• Identify (250 px/m) — sufficient detail to establish identity beyond reasonable doubt from the footage alone. Required for high-security access points, ATM coverage, and evidential quality video.

In this calculator, DORI distances are computed directly from your resolution and focal length: D = (focal length × horizontal pixels) / (required PPM × sensor width). The coloured zones in the top-view diagram map those distances back onto the floor plan so you can see the usable coverage area for each classification at a glance.

Focal Length and Field of View — What Changes When You Zoom In

Focal length has an inverse relationship with field of view. A short focal length (2.8–4mm) gives a wide angle — useful for covering large areas like car parks or open floor plans, but at the cost of pixel density per metre. A longer focal length (12mm, 25mm, or beyond) narrows the FOV and concentrates pixels onto a smaller area, increasing the pixel density at distance and pushing the DORI zones further out.

For most indoor installations, a 2.8–4mm lens on a 1/2.8" sensor covers a typical room adequately. For outdoor perimeter work where you need Identify-level coverage at 30–50m, a 12mm or 25mm varifocal lens on a high-resolution sensor (8MP or 12MP) is typically required. Use the focal length input in this tool to model both scenarios before specifying equipment.

Sensor Format and Its Effect on FOV

Sensor format describes the physical size of the imaging chip. A larger sensor produces a wider field of view at the same focal length. For example, a 4mm lens on a 1/1.8" sensor gives a noticeably wider horizontal angle than the same 4mm lens on a 1/3" sensor.

This is why two cameras listed as "4mm / 4MP" can have different fields of view — the sensor format is the variable that determines coverage. Always check the datasheet and match the sensor size to the calculator for accurate results. The most common formats in current IP security cameras are 1/2.8" and 1/3", with larger 1/1.8" sensors found in premium low-light and multi-megapixel models.

Camera Resolution and Pixel Density

Higher resolution does not increase the field of view — it increases the pixel density within the same area. A 12MP camera with the same lens and sensor as a 4MP camera covers exactly the same scene, but captures three times as many pixels per metre. This directly extends the DORI ranges: an Identify zone that reaches 8m on a 4MP camera might reach 14m on a 12MP camera with the same optics.

The pixel density formula used in this calculator is: PPM = horizontal resolution / (target distance × sensor width / focal length). This is the standard industry formula derived from the relationship between sensor geometry and image plane magnification.

Frequently Asked Questions

What is pixel density (PPM) in CCTV cameras?

Pixels per metre (PPM) is a measure of how many pixels of camera resolution are allocated to each metre of width in the scene at a given distance. A higher PPM means more detail is captured per unit of area — allowing the camera to be used for recognition or identification rather than just detection. The DORI standard defines the minimum PPM required for each classification level.

How do I calculate the field of view of a security camera?

The horizontal field of view angle depends on two things: the physical width of the camera's sensor and the focal length of the lens. A shorter focal length produces a wider angle; a longer focal length narrows it. The coverage width at any given distance then grows proportionally — double the distance, double the coverage width. This calculator applies the standard optical formula automatically when you select sensor format and focal length.

What is the blind spot of a CCTV camera?

The blind spot is the area directly beneath a wall or pole-mounted camera that falls outside the lower edge of the vertical field of view. Its size depends on three factors: how high the camera is mounted, how far it is tilted downward, and how wide its vertical field of view is. A steeper downward tilt reduces the blind spot; a shallower tilt or a narrow vertical FOV increases it. The side-view diagram in this tool shows the blind spot distance for your current settings.

Which focal length should I use for outdoor CCTV?

For wide-area outdoor coverage such as car parks or building perimeters, a 2.8–4mm lens on a high-resolution sensor (8MP+) typically provides the best balance of coverage area and pixel density. For targeted coverage of entrances, gates, or roads at 30–80m range, a 12–25mm varifocal or fixed lens is more appropriate. Model both options using this calculator before finalising your camera specification.

Is this FOV calculator free to use?

Yes — the calculator is completely free with no registration required. It is part of CCTV Design Tool's free toolkit for security installers and system designers. The full design platform — floor plan import, live FOV visualisation, cable routing, and PDF proposals — is also free to get started with.