CCTV Lens Calculator

CCD Size          
Anticipated Target Distance (D)   ft Focal Length Required
Target Area Width (W)   ft mm

Watch Tutorial Videos on how to use the Lens Calculator:

  • PART 1
  • PART 2
  • How to use the CCTV Lens Calculator:

    1. Select the appropriate CCD size from the drop down list. CCD sizes are in inches. Usually the size will be stated, but if you're not sure ask the person you're purchasing it from what the format size is. THIS IS IMPORTANT AS CCD SIZE MAKES A DIFFERENCE!
    2. Enter the distance from the security camera to the target (use number only). You can use units of feet or meters, but you must be sure to use the same units for Width of Target Area.
    3. Enter the Width of the Target Area (field of view) desired. Again, this can be in feet or meters but the units used must be consistent with the units used in the target distance. So for example, if you entered the target distance in feet, the target width must also be in feet. Again, enter numbers only, no text.
    4. Click the ''Calculate' button to calculate the focal length (in mm) of the lens required to achieve the desired field of view at the anticpated target distance.
    5. You may need to experiment with different values of target distance and target width to determine the best choice of focal length and the coverage capabilites of a particular focal length. Fixed focal length lenses (such as the one used in most 'bullet' style cameras) come in standard sizes such as 3.6 mm, 6 mm, and 16 mm. There are also longer focal lengths such as 35 mm, and 50 mm which give higher magnification and greater detail but cover a much smaller area and therefore have a significantly smaller target Width. Remember, larger focal lengths mean greater magnification, but come at the expense of a smaller coverage area (Target Width).
    6. Calculation Example: Let's say you have a 1/3 in. CCD camera. Choose 1/3 from the drop down list. Let's say your distance to the target area is 15 feet and you want to cover an area of 18 feet wide. Enter 15 for 'Distance of Target from Camera' and 18 for the 'Width of Target Area'. Click 'Calculate'. The value returned for focal length required is 4 mm. You could choose a 3.6 mm lens which covers a 20 foot wide area at a distance of 15 feet. Bear in mind that there are other factors in selecting the appropriate focal length beside the width of the target area. You may desire more detail than the 3.6 mm can provide. So, depending on your needs you could choose the 6 mm lens instead, which provides a coverage area of only 12 feet wide at a 15 foot target distance, but would give you higher magnification of the target. If you choose the 6 mm you won't get as wide of a coverage area as the 3.6 mm lens, but you will get greater magnification so you'll need to decide which is better for you based on your specific situation. Alternatively, you might want to have two (or more) cameras, one with a wide angle lens (3.6 mm) for general coverage and another camera with a longer focal length (perhaps a 6 mm or 16 mm) to obtain greater detail in specific areas as needed.

    NOTE: The CCTV Lens Calculator is provided for general information only and is not intended as professional consultation or as a substitute for professional consultation. HowToSurveillance, LLC advises you to seek professional consultation for your individual surveillance needs and shall not be held liable for damages resulting from the use, misuse or unlawful use of the information contained herein.


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