I strive to be readable. I ran a small portion of writings I did
  (1763 sentences, 25,156 syllables...) recently to forums and
  such recently through a "readability" thing and this is what it
  came up with: Readability Formula Grade Flesch-Kincaid Grade
  Level 5.3 Gunning-Fog Score 7.6 Coleman-Liau Index 8.3 SMOG
  Index 6.3 Automated Readability Index 2.8 Average Grade Level
  6.1
  So, what I write, in theory, would be readable by an "average"
  (C student) US 6th grader by their second month of school. Or
  readable by a more advanced 5th grader or much advanced 4th
  grader. Of course, readability indexes must be taken with a
  grain of salt. They're mathematical and they are a very
  skeleton-view of readability, not taking many things into
  account. But still, it shows, to me, that I've thankfully been
  successful at my goal, which is, to the best of my ability try
  to keep my writing as clear as possible. This says nothing of
  style, vocabulary, clarity of logic and such. But it's something
  - at least until artificial intelligence text classifiers
  improve more. They have a VERY long way to go.