FOV Lense Calculator

Distance to Object    ft
Lens Size
Focal Length mm
Field of view (H x V):
ft x ft
Calculate
This handy FOV calculator will help you in determining which lens is right for your application. Simply enter the distance to the object, camera format Example: 1/4, or 1/3 , and focal length of the lens. Click "Calculate" to see the field of view you can expect with that lens. It also works in reverse. If you know the field of view you need, enter it in and the distance to the object along with camera format to find the focal length you will need to get the field of view desired. Surveillance Camera Lens Chart
(approximate values)
Lens
Size
Viewing
Angle
Field of View (in feet)
5 feet
away
10 feet
away
15 feet
away
25 feet
away
50 feet
away
100 feet
away
(mm) Width Height W H W H W H W H W H W H
3.6 74 55 7.5 5.2 15.1 10.4 22.6 15.6 37.7 26.1 75.4 52.1 151 104
4.0 69 49 6.0 4.5 12 9.0 18 13.5 30 22.5 60 45 120 90
4.3 65 45 5.6 4.2 11.2 8.4 16.7 12.6 27.9 20.9 55.8 41.9 111 84
6.0 42 32 3.8 2.9 7.7 5.7 11.5 8.6 19.2 14.4 38.4 28.7 77 57
8.0 32 24 2.9 2.1 5.7 4.3 8.6 6.4 14.4 10.7 28.7 21.3 57 43
12.0 22 17 1.9 1.5 3.9 3.0 5.8 4.5 9.7 7.5 19.4 14.9 39 30
16.0 19 15 1.5 1.2 3.0 2.5 4.5 3.6 7.2 6.1 14.4 12.2 28 24
Here is something which is very important to remember and is a very easy way of thinking about the right Focal length lens.  It is easer to understand this whole field of view thing if you think about it this way.  A wide angle lens at 25 Feet would have a Horizontal field of view of 33.3 Feet  a persons face is only about 8" wide,  8" of a 33.3 Feet field of view is only about 2% of the pixels on that Horizontal line  which means, in the area of the face you only have about 10 pixels .  If a face were 8x8" that's 100 dots.  This is about the limit for facial recognition.

So here is a short cut below.  I have identified the major concerns of people and I have listed the widest horizontal (H) view which is acceptable given the typical resolution of these cameras.
(if you use a camera with a higher resolution then 270,000 pixels you will have better recognition performance.

People are usually concerned about four major objects they want to identify.  I have broken them down here.
#1 Facial Recognition. = 25 Feet Horizontal Field of View
#2 Body Recognition (the ability to Identify someone by how tall they are, if they are male or female,  long or short hair and adult or child =25 Feet to 45 Feet
#3 Licenses Plate Recognition (the ability to actually read the license plate number) = 10 Feet
#4 Car Recognition (the ability to type or make of car) = 60-75 Feet

The function of the lens is to collect light reflected from the scene and focus it into an image onto the CCTV camera sensor.
Most CCTV applications use a fixed-focal-length (FFL) lens, which, like your eye's lens, covers a constant angular field of view (FOV).
S a Fix focal length lens always has the same magnification.
A large variety of CCTV camera lenses are available with different focal lengths (FLs), which will provide different FOVs (magnification).
Wide-angle 3.6mm, medium-angle 6.0mm, or narrow-angle lenses 12.0mm produce different magnifications and FOVs.