Sentence counter

Sentences are counted by their terminating punctuation — full stops, question marks and exclamation marks. Divide the word count by the sentence count and you have the number that actually predicts readability.

Detecting sentences by punctuation is the standard approach and it is approximate by nature. Abbreviations end in full stops and get counted as sentence ends: "Dr. Smith arrived at 9 a.m." reads as three sentences to any rule of this kind, and only a language model knows better. Expect a small over-count in text heavy with abbreviations, decimals or ellipses. The number worth acting on is not the total but the average length — most readability formulas weight words-per-sentence heavily, and prose averaging over twenty-five words a sentence is hard going regardless of vocabulary.