CCTV Lens & FOV Calculator
Calculate CCTV camera field of view and DORI distances. Enter sensor format, resolution, and lens focal length to get HFOV/VFOV angles and Detect, Observe, Recognize, and Identify ranges in feet per EN/IEC 62676-4. Free, no sign-up.
What to calculate next
Tools commonly used alongside this calculation
CCTV / NVR Storage Calculator
Calculate CCTV / NVR storage and bandwidth. Add IP cameras by resolution and codec (H.264/H.265) to get the hard drive size in TB for your retention days, plus the total network bandwidth. Free, no sign-up.
PoE Power Budget Calculator
Check a PoE switch power budget per IEEE 802.3af/at/bt. Add powered devices by type and PD class to total the watts drawn, see the utilization and headroom, and confirm the load fits the switch budget and port count. Free, no sign-up.
Fiber Optic Loss Budget Calculator
Calculate a fiber optic link loss budget per TIA-568 and FOA. Add fiber length, connectors, and splices to total the cable plant loss in dB, then compare it to the transceiver power budget for the link margin and pass/fail. Free, no sign-up.
Explanation
A CCTV lens calculator turns a camera’s lens focal length, sensor size, and resolution into a usable answer: how wide an area the camera sees, and how far away it can still detect, recognize, or identify a person. The two drivers are the angle of view, set by the lens and sensor, and the pixel density on the target — the number of pixels that land on a face or figure at a given distance. This tool reports both, plus the four DORI ranges from the EN/IEC 62676-4 standard, in feet or metres.
Focal length, sensor, and field of view
Focal length and sensor width set the horizontal angle of view (HFOV). A short focal length (2.8–4 mm) gives a wide angle for an overview; a long one (12 mm and up) narrows the view and concentrates pixels for distance. The width of the scene a camera covers grows linearly with distance.
FOV width at distance D = D × sensor_width ÷ focal_length
The active sensor width depends on the optical format and the resolution’s aspect ratio, so a 16:9 and a 4:3 sensor of the same “type” do not have the same width. This calculator derives the true width from the format diagonal and your resolution rather than assuming a fixed value.
| Symbol | Meaning |
|---|---|
| focal_length | Lens focal length (mm) |
| sensor_width | Active image-sensor width (mm) |
| D | Distance from camera to target |
DORI: detect, observe, recognize, identify
DORI ties four named tasks to four pixel densities on the target plane. As a target moves away, the pixels covering it drop, so each task has a maximum distance. Horizontal pixel density is the resolution divided by the field-of-view width at that distance, which gives the DORI range directly.
DORI distance = horizontal_pixels × focal_length ÷ (required_px/m × sensor_width)
| Task | Pixels / metre | Pixels / foot | What you can tell |
|---|---|---|---|
| Detection | 25 | 8 | A person is present |
| Observation | 62.5 | 19 | Some characteristic details |
| Recognition | 125 | 38 | Whether it is someone known |
| Identification | 250 | 76 | Identify an unknown face |
250 px/m for identification works out to about 76 pixels per foot. Public tenders and insurers often cite these EN/IEC 62676-4 numbers as acceptance criteria.
Choosing a lens and reading the results
Decide the task first. To identify faces at an entrance, work back from the identification range; for a wide parking-lot overview, a short focal length with detection-only coverage may be enough. Higher resolution pushes every DORI range farther for the same lens, which is the real payoff of moving from 2 MP to 4K. After fixing the lens, size the rest of the install: the CCTV / NVR storage calculator sizes the recording drive in terabytes, and the PoE power budget calculator confirms the switch can power every camera over Ethernet.
Assumptions and limitations
DORI ranges assume an undistorted lens, an in-focus image, and good lighting. Wide-angle lenses add barrel distortion at the edges, low light and IR cut effective resolution, and compression artifacts reduce real detail below the raw pixel count. Sensor diagonals follow the optical “type” convention and vary slightly between manufacturers — treat the output as a design estimate and confirm against the camera maker’s own coverage data for acceptance.
When several cameras share one run back to the head end, the aggregate traffic also drives the network backbone — the fiber optic loss budget calculator checks the uplink has enough optical margin for that load.