To implement the Frye index, the user counts the total number of syllables and sentences in the selected passage. Abbreviations are counted as their whole-word equivalents. The user also counts the number of sentences. Lists are counted as one sentence if items are separated by semicolons or commas, but as separate sentences if each bullet point starts with a capital letter and ends with a period.
The word and syllable counts are scored by using the Frye readability grid. Users find the intersection of the average number of syllables per 100 words and the average number of sentences per 100 words. As an example, if a passage has 163 syllables and five sentences, the intersection of these two points corresponds with a 12th grade reading level.
If a wide discrepancy exists between the readability of different sections of the piece of writing, the readability is deemed to be uneven. The readability index has a floor of grade 1 and a ceiling of college level; scores below or above these points are not calculated.
The Frye readability index has been validated against primary and secondary school reading material and produces a result comparable with other readability formulas. The index is used for written materials targeted to a specific population, such as sixth-graders, elementary school pupils or college-age students. Job applications and newspapers, for example, are typically written at or below the eighth-grade level.