Free tool · UK
CCTV lens calculator
Use it before the camera is mounted. Input: focal length, sensor size, resolution and distance. Output: horizontal angle of view, width of the scene in metres, and pixel density in pixels per metre. The pixel density is then checked against the four DORI detail thresholds.
Field of view
85°
horizontal angle
Scene width at 10m
18.2 m
what the frame covers
Detail level
141 ppm
Recognise: sufficient for a known person or a number plate
| DORI level | Needs | This setup |
|---|---|---|
| Identify | ≥ 250 ppm | up to ~5.6 m |
| Recognise | ≥ 125 ppm | Yes |
| Observe | ≥ 62 ppm | Yes |
| Detect | ≥ 25 ppm | Yes |
Stocked cameras at 2.8 mm
- 2.8 mm fixedHikvision 5 MP PIR Fixed Turret Camera£27.40
- 2.8 mm fixedHikvision 5 MP Audio Fixed Turret Camera£29.58
- 2.8 mm fixedHikvision 4K Fixed Turret Camera£38.49
- 2.8 mm fixedHIKVISION 3K ColorVu PIR Siren Fixed Bullet Camera£40.59
- 2.8 mm fixedHikvision 3K Two Way Audio & Siren Fixed Bullet Camera£43.99
- 2.8 mm fixedHikvision 3K Two Way Audio Fixed Turret£43.99
The calculation uses the sensor selected above. Confirm the sensor size on each camera’s product page. Rule: at equal focal length, field of view increases with sensor width (wider sensor, wider field).
How to read the output
Focal length trades coverage against detail. A 2.8mm lens covers a wide area at low detail; a 12mm lens covers a narrow area and resolves detail at distance. IEC 62676-4 defines the DORI thresholds in pixels per metre: Identify (a stranger) 250, Recognise (a known person, or a number plate) 125, Observe (what happened) 62, Detect (movement) 25.
Recommended layout. Entrance: wide lens, for context. Approach: narrower lens or higher-resolution camera, for identification. Where one camera must cover both, specify a varifocal model and set the focal length on site.