Security camera distance calculator
Enter a camera's resolution and lens to get how far it can identify, recognize, observe and detect a person, the pixels per foot at your distance, and the lens or resolution that would do the job.
Assumptions typical values, with the reason for each
Typical: 15°. Camera makers' installation guides put a face camera at about 15 to 20 degrees down, and no steeper than about 30.
For a site rule of your own, such as 300 px/m at a register. 1 px/ft = 3.28 px/m.
- Face width, 16 cm
- Typical. The width IEC 62676-4 bases its levels on; used for pixels across a face.
- Person height, 5.75 ft
- Typical adult height, used for how tall a person is in the image.
- Flat-scene formula
- Density is averaged across the full image width, so it is the conservative number. Spec sheet DORI distances are measured at the image center and can read longer for wide lenses.
Short of identify. Needs 76.2 px/ft: a lens of 57.9° or narrower (6 mm, about 50°), or 3,879 px across at 80° (12MP, 4:3).
An estimate from the inputs above; a site survey sets the real numbers.
The breakdown
At your target
What the job takes at that distance
Mounting height and angle
Usable zone: From 16.8 ft to 19.5 ft along the floor, where the angle is under 15° and the camera can identify.
At night
Every level for this camera 4MP, 2,560 × 1,440 px · 80°
| Level | Density | From the lens | Along the floor | View width |
|---|---|---|---|---|
| Identify | 250 px/m · 76.2 px/ft | 20.0 ft | 19.5 ft | 33.6 ft |
| Recognize | 125 px/m · 38.1 px/ft | 40.0 ft | 39.8 ft | 67.2 ft |
| Observe | 62 px/m · 18.9 px/ft | 80.7 ft | 80.6 ft | 135 ft |
| Detect | 25 px/m · 7.6 px/ft | 200 ft | 200 ft | 336 ft |
| Overview 2025 edition | 20 px/m · 6.1 px/ft | 250 ft | 250 ft | 420 ft |
| Outline 2025 edition | 40 px/m · 12.2 px/ft | 125 ft | 125 ft | 210 ft |
| Discern 2025 edition | 80 px/m · 24.4 px/ft | 62.6 ft | 62.4 ft | 105 ft |
| Perceive 2025 edition | 125 px/m · 38.1 px/ft | 40.0 ft | 39.8 ft | 67.2 ft |
| Characterize 2025 edition | 250 px/m · 76.2 px/ft | 20.0 ft | 19.5 ft | 33.6 ft |
| Validate 2025 edition | 500 px/m · 152.4 px/ft | 10.0 ft | 8.9 ft | 16.8 ft |
| Scrutinize 2025 edition | 1,500 px/m · 457.2 px/ft | 3.3 ft | 0.0 ft | 5.6 ft |
Show the math
- Half the view angle: 80° ÷ 2 = 40°, and tan 40° = 0.8391
- Identify needs 250 px/m × 0.3048 = 76.2 px/ft
- Identify reach = 2,560 ÷ (2 × 0.8391 × 76.2) = 20.0 ft from the lens
- Along the floor = √(20.0² - 4.5²) = 19.5 ft
- Line of sight to the target = √(30.0² + 4.5²) = 30.3 ft
- View width there = 2 × 30.3 × 0.8391 = 50.9 ft
- Density = 2,560 px ÷ 50.9 ft = 50.3 px/ft, Recognize
- Angle = atan(4.5 ÷ 30.0) = 8.5°
- Widest lens for identify there = 2 × atan(2,560 ÷ (2 × 30.3 × 76.2)) = 57.9°
- Pixels needed at this lens = 76.2 × 50.9 = 3,879 px
- Identify strip = 2,560 ÷ 76.2 = 33.6 ft
- Face angle limit 15°: steeper than that out to 4.5 ÷ tan 15° = 16.8 ft
How to use the camera distance calculator
- Pick the camera by its pixel width. Choose a resolution, or Custom for the pixel size on the spec sheet.
- Set the lens. Tap a typical lens or type the horizontal field of view in degrees.
- Name the job and the place. Choose identify, recognize, observe or detect, then enter the distance along the floor and the two heights.
- Read the answer. The big number is the reach for that job; the verdict says whether it works at your distance and, if not, what lens or pixel width would.
- Keep it. Copy the link to reopen this exact case.
How the pixels per foot calculation works
Every number comes from three lines of geometry, the same math as our guide to how far a security camera can see.
View width at distance d = 2 × d × tan(horizontal field of view ÷ 2)
Pixels per foot = horizontal pixels ÷ view width in feet
Reach of a level = horizontal pixels ÷ (2 × tan(field of view ÷ 2) × pixels per foot it needs)
The levels are from IEC 62676-4:2014: identify at 250 pixels per meter (76.2 per foot), recognize at 125 (38.1), observe at 62 (18.9) and detect at 25 (7.6). The 2025 edition adds validate at 500 px/m and scrutinize at 1,500, used for license plates.
The distance d is the line of sight from the lens: √(floor distance² + height difference²). The angle to a face is checked against the 15 to 30 degree guidance in camera makers' installation guides, and IR light falls with the square of the distance. Density is averaged across the image, so the answer is conservative; fisheye lenses are not modeled.
Worked example: a front door face camera
The Front door example: a 4MP camera, 2,560 pixels wide, with a 4 mm lens about 80 degrees wide, 8 ft up inside the door and aimed at faces 10 ft away.
- The camera is 8 ft up and the face 5.5 ft, so the height difference is 2.5 ft and the line of sight is √(10² + 2.5²) = 10.3 ft.
- The view there is 2 × 10.3 × tan 40° = 17.3 ft wide.
- 2,560 pixels ÷ 17.3 ft = 148 pixels per foot, about 1.9 times the 76.2 that identify needs. A face is about 78 pixels across.
- The angle down to the face is atan(2.5 ÷ 10) = 14.0 degrees, inside the 15 degree guidance.
- It identifies to 20.0 ft from the lens; with the 15 degree limit, faces are usable from 9.3 ft to 19.9 ft along the floor.
Typical identify distances by lens and camera
| Lens, typical angle | 2MP, 1,920 px | 4MP, 2,560 px | 4K, 3,840 px | View width at 20 ft |
|---|---|---|---|---|
| 2.8 mm, about 100° | 10.6 | 14.1 | 21.1 | 47.7 |
| 4 mm, about 80° | 15.0 | 20.0 | 30.0 | 33.6 |
| 6 mm, about 50° | 27.0 | 36.0 | 54.0 | 18.7 |
| 8 mm, about 40° | 34.6 | 46.2 | 69.2 | 14.6 |
| 12 mm, about 26° | 54.6 | 72.8 | 109.1 | 9.2 |
Typical angles for small-sensor fixed cameras; read the real angle from the spec sheet. Recognize is twice each distance, observe about four times and detect ten times.
Common mistakes when sizing camera distance
- Reading megapixels as reach. 4K has four times the pixels of 1080p but only twice the width, so with the same lens it identifies twice as far, not four times.
- Taking the IR rating as the identify range. A 200 ft IR rating says how far the light reaches, not how far the camera identifies.
- Mounting the face camera high. From 12 ft up, the angle to a face stays steeper than 15 degrees out to about 24 ft, past where that camera can identify.
- Expecting one wide camera to identify across a wide entrance. At its identify limit a 4MP camera covers a strip about 34 ft wide whatever the lens. A 60 ft storefront takes two cameras or more pixels.
- Planning at the exact minimum. 250 px/m is a floor; compression, blur and poor light all take detail away.
Camera distance questions
How far can a security camera see?
It depends on the job. A typical 4MP camera with a 4 mm lens, about 80 degrees wide, identifies a face to about 20 ft, recognizes someone to about 40 ft, observes what a person is doing to about 81 ft and detects a person to about 200 ft. A narrower lens or more horizontal pixels pushes every distance out.
How do you calculate pixels per foot for a security camera?
Divide the camera's horizontal pixels by the width of the view at the target, in feet. The view width is 2 × distance × tan(half the horizontal field of view). A 2,560 pixel camera with an 80 degree lens sees 33.6 ft across at 20 ft, so it puts about 76 pixels on each foot.
How many pixels per foot do you need to identify a face?
IEC 62676-4:2014 puts identify at 250 pixels per meter, about 76 per foot. Recognize needs 125 (38 per foot), observe 62 (19) and detect 25 (8). Treat 76 as the minimum for a face, not a target to hit exactly.
How wide can a CCTV camera see?
Most fixed cameras with a standard wide lens see 80 to 110 degrees across, narrower lenses 25 to 50 degrees, and fisheye or panoramic cameras up to 180 or 360 degrees. At 50 ft, a 100 degree lens sees about 119 ft across and a 40 degree lens about 36 ft. A wider view always means fewer pixels on each foot of it.
How far can a 4K security camera see?
A 4K camera is 3,840 pixels wide. With a typical 2.8 mm lens, about 100 degrees wide, it identifies faces to about 21 ft, recognizes people to about 42 ft and detects a person to about 211 ft. With a 12 mm lens, about 26 degrees wide, it identifies to about 109 ft, but the view there is only about 50 ft across.
Sources and standards
- IEC 62676-4:2014Application guidelines for video surveillance: Detect 25 px/m, Observe 62, Recognize 125, Identify 250.
- IEC 62676-4:2025Second edition: Overview 20 px/m, Outline 40, Discern 80, Perceive 125, Characterize 250, Validate 500, Scrutinize 1,500.
- Camera makers' installation guidesFace capture at a downward angle of about 15 to 20 degrees, and no more than about 30.
- Geometry and the inverse square lawView width = 2 × d × tan(HFOV ÷ 2); light from a small source falls with the square of the distance.
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