How to Calculate Fog Index

1) Take a typical section of approximately 100 words.

2) Count the number of words, not counting proper names and counting hyphenated words as one word.

3) Count the number of sentences and divide it into the number of words to get the average number of words per sentence. Call this number 'X'.

4) Count the number of words with three syllables or more. Call this number 'Y'. Do not count words that reach three syllables by changing a part of speech (for example plurals or verb tenses, so the word 'achieving" would not count, as its third syllable is due to its tense).

5) The fog index is the average number of words per sentence (X), plus the number of words of three syllables or more per 100 words (Y), multiplied by two fifths.

6) Fog Index = (X + Y) * 0.4

7) Clear writing has a fog index of between nine and twelve. In tabloids it can be as low as five. Aim to keep it below ten.