CCTV Lens & Field-of-View Calculator

What this tool will do

• FoV in degrees + feet at any distance for any IP camera + lens combination
• Multi-vendor sensor library — accurate mm dimensions for 1/4″, 1/3″, 1/2″, 1/1.8″, 1″, 4/3″ across Hikvision, Axis, Bosch, Dahua, Avigilon, Reolink, Uniview
• Visual coverage diagram with mount-height shadow and floor footprint
• Reverse-solve: "what lens gives me 30 ft of coverage at 25 ft distance?"
• Pixel-density cross-check — flag if your lens choice produces sub-forensic PPF at the target distance

Frequently asked questions

How do I calculate field of view for a CCTV camera?

Field of view depends on three things: sensor width (mm), lens focal length (mm), and distance to subject. The horizontal angle of view is 2 × atan(sensor_width / (2 × focal_length)); horizontal coverage at distance D is 2 × D × tan(angle ÷ 2). The catch: sensor width varies by camera model even within the same nominal format (e.g. "1/3 inch"), which is why one-vendor-only calculators give wrong answers for mixed-vendor designs.

What focal length lens do I need for 100 feet?

For a 1/3'' sensor (~4.8 mm wide) covering ~30 ft of scene at 100 ft distance, plan for ~16 mm focal length. For face-identification PPF (≥80 ppf) at 100 ft on a 4 MP camera, push to 25–35 mm. Reverse-solving from coverage requirements is the right path — guessing focal lengths and checking is what makes vendor calculators frustrating.

What's the difference between 1/3 inch and 1/2.8 inch sensors?

1/3'' sensors run ~4.8 mm × 3.6 mm; 1/2.8'' sensors run ~5.0 mm × 3.7 mm — about 5–8% wider per side. At the same focal length, the larger sensor sees ~5% more horizontal coverage and resolves slightly fewer pixels-per-foot at the same target. The label difference is small; the actual physical difference is small too — but vendors mix them across product lines, so verifying the actual mm matters more than reading the format label.

How do I choose a lens for a CCTV camera?

Start from coverage requirements at distance, not focal length. Pick a target (face ID at 25 ft, license plate at 50 ft, general detection at 100 ft) and reverse-solve the focal length from sensor size and PPF target. Verify the lens choice doesn't drop you below forensic PPF — many vendor calculators stop at FoV without flagging when the lens choice fails identify-zone pixel density.

What is a varifocal lens and when should I use one?

A varifocal lens has a manually adjustable focal length range (e.g. 2.8–12 mm) — you tune it on-site to match actual coverage needs. Use varifocals when (a) the install distance isn't pinned at design time, (b) you're standardizing one camera SKU across varied scenes, or (c) you want field-tunable coverage without re-ordering hardware. Trade-off: varifocals usually have slightly worse low-light performance than equivalent fixed-focal lenses at the same price tier.