Security cameras · pixel density
Camera pixel density calculator.
See the pixels per metre a camera gives at a distance and the farthest distance for each guideline target.
Inputs
Pixel density
Enter the numbers above.
What is pixel density for security cameras?
Pixel density, in pixels per metre (PPM), is how many horizontal pixels fall on each metre of the scene at the subject's distance. It is the horizontal resolution divided by the scene width, and the scene width is 2 x distance x tan(half the field of view). Higher PPM means more detail on a face or number plate. Design guides commonly quote about 250 PPM to identify a person, 125 PPM to recognise someone you know and 62 PPM to observe or detect activity; these are guideline targets, not requirements you can read from a standard we opened, so the tool lets you edit them.
Worked example. A 2560-pixel-wide camera with a 90 degree horizontal field of view sees a scene 2 x 10 x tan(45) = 20.0 m wide at 10 m, giving 2560 / 20 = 128 px/m, which meets the 125 recognition target but not 250. Identification at 250 needs a distance of up to 5.1 m, recognition up to 10.2 m and observation up to 20.6 m.
These figures use the centre of the frame and ignore lens distortion, motion blur, lighting and angle, all of which reduce usable detail. Treat the result as a planning aid.
Frequently asked questions
What is a good pixels per metre for facial identification?
About 250 px/m is the figure commonly quoted for identification, and the tool uses it as an editable default. It is a guideline, not a legal or standards requirement we could verify.
How do I calculate pixels per metre?
Scene width at the distance is 2 x distance x tan(half the horizontal field of view); divide the horizontal pixels by it. A 2560 px camera at 90 degrees and 10 m gives 128 px/m.
Does a higher resolution camera always help?
Only if the field of view stays the same or narrows. Doubling pixels doubles PPM, but widening the lens to cover more ground cuts it again.
Why does the tool say it is only a guideline?
Real image quality also depends on light, angle, blur and compression, so a camera that meets a target on paper can still miss it in practice.
Sources
Checked
- Wikipedia, "Angle of view (photography)", opened 8 October 2026. angle of view = 2 arctan(d / 2f) for rectilinear lenses, d = sensor size, f = focal length
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Scope
Guideline arithmetic only. It is not a security design or a legal compliance check; requirements for cameras vary by place and use. The 250, 125 and 62 px/m targets are commonly quoted guideline values, not text we opened from a standard.