The most readable text is one that you know all the vocabulary, and the sentences are not too long for your level of comprehension.
It's important that grade level reading comprehension skill can vary widely throughout the day. Early in the morning, when your mind is bright and fresh, you comprehension is at the highest. Late at night, when tired, your comprehension dips to a low point. Many students of foreign languages notice that when tired understanding a foreign language can be exceptionally difficult.
The Readability grade level scores given for each section of text are calculated using the RIX formula. The RIX formula can be used on documents of most Western European Languages
RIX = (Long Words / Sentences)
In this formula, a word is considered long when its number of characters is six or greater. The ratio of these two values provides the ranking. The table below provides a breakdown of how the ratio maps to a grade level comprehension.
| Ratio | Grade Level |
| 7.2+ | College |
| 6.2+ | 12 |
| 5.3+ | 11 |
| 4.5+ | 10 |
| 3.7+ | 9 |
| 3.0+ | 8 |
| 2.4+ | 7 |
| 1.8+ | 6 |
| 1.3+ | 5 |
| 0.8+ | 4 |
| 0.5+ | 3 |
| 0.2+ | 2 |
| 0 to 0.2 | 1 |