These tests use formulae to calculate how ‘easy’ a document is to read, with the answer relating to a readability index. One example of a formula is [4.71 x (characters / words)] + [0.5 x (words / sentences)] – 21.43. A simpler method is to structure your writing for a 12 year old. By doing this, you will ensure that all stressed, time-poor or distracted readers will be able to understand your key messages.
There are several tests which gauge the readability of a document. These include Flesch-Kincaid, ARI and Coleman-Liau.