How Long Should a Sentence Be? Find and Fix Long Sentences

Most readable writing averages 15 to 20 words per sentence, with individual sentences that occasionally run longer, and anything past about 25 to 30 words is worth a second look. You don't need to count by hand: paste your draft into the Sentence Length Checker and it shows the average, the median and every sentence over your limit, highlighted where it sits in the text.

Why sentence length matters

A reader has to hold the start of a sentence in their head until the point arrives. Long sentences make them juggle clauses and qualifiers, and on a phone a 45-word sentence can fill the screen. Plain-language guides give the same advice: keep the average low, split the outliers and vary the rhythm.

Variety matters. A page of nothing but eight-word sentences reads like a list of instructions. The goal is to make long sentences rare and deliberate, not to ban them.

What the numbers tell you

After you paste your text, the checker shows four figures:

• Sentences: how many it found.
• Average length: total words divided by the number of sentences, to one decimal place.
• Median length: the middle value when every sentence is lined up from shortest to longest.
• Over the limit: how many sentences are longer than your word limit, and what share of the total that is.

Below those, four small tiles sort sentences into groups of 1–10, 11–20, 21–30 and 31 or more words, so you can see the spread at a glance.

The median is easy to overlook. One 70-word monster can drag the average up while most sentences are fine. When the average is much higher than the median, a few very long sentences are to blame. When both are high, long sentences are a habit.

A worked example

Imagine a six-sentence paragraph whose sentences are 9, 14, 17, 22, 28 and 40 words long.

• Average: 9 + 14 + 17 + 22 + 28 + 40 = 130 words, and 130 ÷ 6 ≈ 21.7 words.
• Median: with an even count, it's the mean of the two middle values, 17 and 22, so 19.5 words.
• Over 25 words: two sentences, the 28 and the 40, which is 2 of 6, or 33%.
• Groups: one sentence in 1–10, two in 11–20, two in 21–30 and one in 31+.

The 28-word sentence is highlighted in amber because it's over the 25-word limit. The 40-word one turns red, because the checker uses red for anything over one and a half times the limit, here 37.5 words. Splitting that single 40-word sentence into two of 20 would bring the average to 130 ÷ 7 ≈ 18.6 words.

How to check your writing step by step

1. Paste your text into the box.
2. Set Flag sentences longer than to the limit you want. It starts at 25, which is a common guide for web writing. Plain-language guides often suggest 20. The lowest limit you can set is 5.
3. Read the stats and the length groups to judge the overall picture.
4. Use Previous and Next to step through each highlighted sentence in context. A counter shows which one you're on.
5. Check Longest sentences at the bottom. It lists the five longest, each with its word count, which is usually the best place to start editing.

If nothing is over the limit, a green notice says so. Your text stays in your browser and isn't saved.

How are sentences detected?

The checker uses rules rather than grammar analysis. A sentence ends at a full stop, question mark or exclamation mark followed by a space and a capital letter, or at a blank line. It knows to skip the full stop in common abbreviations such as "Dr.", "e.g." and "etc.", in initials like "J. R. Jones" and in decimals such as 3.50. For example, "Dr. Smith paid $3.50 for coffee, e.g. a latte. J. R. Jones agreed. It was fine." is read as exactly three sentences.

Because it's a heuristic, some layouts confuse it. Bulleted text and long quotations can split or merge in unexpected places, so treat the numbers as a strong guide rather than an exact count.

Four ways to fix a long sentence

• Split at "and", "but" or "which". They often join two complete thoughts.
• Move side notes out. A clause in parentheses or dashes can become its own sentence or go.
• Turn a series into a list. Four or more items with explanations scan better as bullets.
• Cut the warm-up. Phrases like "It is important to note that" add words without adding meaning.

Related tools

For an overall difficulty grade that combines sentence length with word length, try the Readability Score tool. For plain totals, the Sentence Counter and Word Counter are quicker. The Duplicate Word Finder catches the "the the" typos that creep in when you rewrite.

FAQ

Why does the checker count a heading as a sentence?

Any text followed by a blank line is treated as its own sentence, whether or not it ends with punctuation. Leave headings out of what you paste if you want the averages to reflect only your paragraphs.

How are words counted inside a sentence?

Runs of letters and numbers count as words. Contractions and hyphenated words count once, and a decimal like 3.50 is a single word.

Paste your next draft into the Sentence Length Checker and see which sentences need a break.