Can someone explain: "Total Area" and "% Area"?

I created a test image with a black block which is 25% of the image size. I converted it to 8bit, did threshold, and then “Analyze Particles”. The summary showed 1 particle but the “Total Area” shows as 0.401 while the %Area shows approx 25%. Why isn’t Total Area showing 0.25?

The total area is the area of the selection in calibrated units. Your image is 1.3 x 1.21 inches (see top of image), so its total area is 1.573 square inches. Your square is approximately 0.65 x 0.605 inches resulting in a total area of 0.39 square inches, i.e. the value of 0.407 that you get in the results table (allowing for the square not to be exactly 25% of the whole image).
Hope this helps,


Yes, it helps very much!

Thank you for your reply and for your knowledge,