Enter the pixel size (um) and the focal length (mm) into the Calculator. The calculator will evaluate the Arc Seconds Per Pixel. 

Arc Seconds Per Pixel Formula

ASPP = (PS/FL) * 206.265


  • ASPP is the Arc Seconds Per Pixel (arc-sec/pixel)
  • PS is the pixel size (um)
  • FL is the focal length (mm)

To calculate Arc Seconds Per Pixel, divide the pixel size by the focal length, then multiply by 206.265.

How to Calculate Arc Seconds Per Pixel?

The following steps outline how to calculate the Arc Seconds Per Pixel.

  1. First, determine the pixel size (um). 
  2. Next, determine the focal length (mm). 
  3. Next, gather the formula from above = ASPP = (PS/FL) * 206.265.
  4. Finally, calculate the Arc Seconds Per Pixel.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

pixel size (um) = 75

focal length (mm) = 90