Sentence Counter
Count sentences and calculate average sentence length in any text. Enter values for instant results with step-by-step formulas.
Reviewed by Daniel Agrici, Founder & Lead Developer
Formula
Flesch Reading Ease = 206.835 - 1.015(words/sentences) - 84.6(syllables/words)
Sentences are counted by terminal punctuation marks. The Flesch Reading Ease score combines average sentence length and syllable density to estimate readability on a 0-100 scale. The Flesch-Kincaid Grade Level converts this to a US school grade.
Worked Examples
Example 1: Short Paragraph Analysis
Problem:Analyze: "The quick brown fox jumps over the lazy dog. It was a sunny day. The dog slept peacefully."
Solution:Sentences: 3 (each ending with a period)\nWords: 18 total\nAverage words per sentence: 18 / 3 = 6.0\nCharacters: 82 (no spaces: 68)\nSyllables: approximately 21\nFlesch Reading Ease: 206.835 - 1.015(6) - 84.6(1.17) = 101.8 (capped at 100)
Result:Sentences: 3 | Words: 18 | Avg: 6.0 words/sentence | Very Easy readability
Example 2: Complex Academic Text
Problem:Analyze: "The epistemological foundations of contemporary educational theory necessitate a comprehensive understanding of pedagogical methodologies. Furthermore, the integration of interdisciplinary approaches facilitates enhanced cognitive development."
Solution:Sentences: 2\nWords: 25 total\nAverage words per sentence: 25 / 2 = 12.5\nTotal syllables: approximately 62\nFlesch Reading Ease: 206.835 - 1.015(12.5) - 84.6(2.48) = -3.4 (clamped to 0)
Result:Sentences: 2 | Words: 25 | Avg: 12.5 words/sentence | Very Difficult readability
Frequently Asked Questions
How does the sentence counter identify sentences?
This sentence counter identifies sentences by detecting sentence-ending punctuation marks including periods, exclamation marks, and question marks. The algorithm handles common edge cases such as abbreviations and decimal numbers to some extent, though complex abbreviations like U.S.A. or Mr. may occasionally affect the count. Each sequence of text terminated by one or more sentence-ending punctuation marks is counted as one sentence. If the text ends without terminal punctuation, the remaining text is counted as an additional sentence. For the most accurate count, ensure your text uses standard punctuation conventions. The counter works with English text and may produce different results with languages that use different punctuation rules.
What is a good average sentence length for readability?
Research on readability consistently shows that shorter sentences are easier to understand. The average sentence length in published English prose is approximately 15 to 20 words. For web content and journalism, experts recommend keeping the average between 14 and 18 words per sentence. Academic and technical writing typically averages 20 to 30 words per sentence. Legal documents often exceed 30 words per sentence, contributing to their reputation for being difficult to read. However, variation is important. A mix of short punchy sentences and longer more complex ones creates rhythm and keeps readers engaged. Consistently uniform sentence length makes writing feel monotonous regardless of whether sentences are all short or all long.
References
Reviewed by Daniel Agrici, Founder & Lead Developer · Editorial policy