How to use the sentence length analyzer
- Paste your draft.
- Set the word limit above which a sentence is flagged as long.
- Read the number of sentences, the average, the median and the spread of their lengths.
- Use the length groups and the list of the longest sentences to find places to split or vary.
Formula
sentence length = number of words in the sentence
average = total words / number of sentences
median = the middle length when sentences are sorted
standard deviation = square root of the mean of (length - average)^2
The standard deviation here is the population value. A higher number means the lengths vary more, which usually reads as more varied rhythm.
A short memo
A memo has five sentences of 5, 24, 1, 5 and 5 words, 40 words in all. The average is 8 words, the median is 5, and the standard deviation is 8.15. The longest sentence has 24 words and, with a limit of 25, none is flagged as long.
Four of the five sentences fall in the 1 to 5 word group (80 percent) and one in the 21 to 25 word group. The sentence Questions go to Dr. Lee. counts as one sentence of 5 words, because Dr. is recognized as an abbreviation. Five sentences of 3 or 4 words give an average of 3.6 and a spread of only 0.49, which reads as steady and choppy.
Rhythm and readability
Writing that uses sentences of nearly the same length can feel flat, and writing that only uses very long sentences is hard to follow. A mix of short and medium sentences with an occasional long one tends to read well. The average alone hides this, so look at the spread and the groups too.
There is no single right number. A legal notice, a product description and a story all work differently, and quotations and lists can distort the counts. Use the page to see your draft more objectively, then decide.
How sentences are found
A sentence ends at a period, exclamation mark or question mark followed by a space, or at the end of a paragraph. Common abbreviations such as Dr. and Mr., single capital initials and a period followed by a lowercase letter do not end a sentence. Odd cases can be miscounted, so check the list of the longest sentences. For reading level, use the Readability Score Calculator. To count words and reading time, use the Word Counter, and to find repeated words, use the Repeated Word Finder.
Assumptions and limits
- A word is a run of letters or digits, with an inner apostrophe, hyphen, comma or period kept inside it.
- Headings and list items count as sentences if they are on their own lines.
- Text is limited to 100,000 characters.
- The word limit shown when the page opens is an example. Set the limit that fits your style guide.
Frequently asked questions
What is a good average sentence length?
It depends on the kind of writing. Plain-language guides often favor averages in the teens, but the right number for your readers and topic is a choice, not a rule.
Why does the page count Dr. Lee as one sentence?
Common abbreviations are recognized so that their period does not end a sentence. A single capital letter followed by a period, as in an initial, is treated the same way.
What is the standard deviation telling me?
It says how far lengths usually fall from the average. A small value means sentences are similar in length, and a large one means a mix of short and long.
Does it work for other languages?
It counts words by letters and digits, so it works for many languages that use spaces between words. It will not work well for languages written without spaces.