Average Sentence Length: A Readability Checklist

A good average sentence length for web pages, emails and business writing is 15–20 words. Above about 25, readers start rereading lines, and comprehension drops. The fastest way to find out where you stand is to count sentences, divide your word count by that number, and then fix the longest sentences first.

This guide turns that into a checklist you can run on any draft in a few minutes.

How is average sentence length calculated?

Average sentence length is simply total words divided by total sentences. A 300-word email with 12 sentences averages 25 words per sentence. The same 300 words split into 18 sentences averages 16.7.

The Sentence Counter does this math for you. Paste your text and the top row shows Sentences, Paragraphs, Words per sentence (rounded to one decimal) and Words.

What counts as a sentence break?

The counter ends a sentence at a period, question mark, exclamation mark or ellipsis (…) followed by a space, or at a blank line. That means headings and list items separated by blank lines count as their own sentences, which is usually what you want.

It also means abbreviations can inflate the count. This line:

Dr. Smith arrived at 3 p.m. on Monday. e.g. this.

is counted as five sentences, not two, because "Dr." and "p.m." are each followed by a space. If your text is full of abbreviations, the average will look shorter than it really is. Keep that in mind for academic or medical writing.

The readability checklist

Run through these in order. Each step takes a minute or two.

1. Get your baseline. Paste the draft and note Words per sentence. Under 20? You can probably stop at step 4.
2. Find the monsters. Scan for any sentence that runs longer than three lines on screen. Those are usually 35+ words and drag the average up on their own.
3. Split at the conjunction. Long sentences often hinge on "and", "but", "which" or "because". Replace one with a period and start a new sentence.
4. Check paragraph length. Compare Sentences to Paragraphs. More than five sentences per paragraph on the web is a wall of text; break it up.
5. Vary the rhythm. An average of 16 is good. Every sentence being exactly 16 words is monotonous. Mix a few short sentences with medium ones.
6. Recount. Paste the edited version and confirm the average moved.

A before-and-after example

Before (one sentence, 47 words):

We are writing to let you know that because of the scheduled maintenance that our infrastructure team will be carrying out on Saturday evening, the customer portal will be unavailable for approximately four hours, and we recommend that you complete any urgent transactions before Friday at noon.

After (three sentences, 34 words, about 11.3 words per sentence):

Our customer portal will be unavailable for about four hours on Saturday evening while our team carries out scheduled maintenance. Please complete any urgent transactions before Friday at noon. We're sorry for the inconvenience.

Same information, 13 fewer words, and every sentence is easy to scan. The key move was putting the consequence (portal down) first and splitting the request into its own sentence.

When a high average is fine

Not every text should hit 15–20. Legal clauses, technical specifications and academic arguments sometimes need long sentences to stay precise. Fiction uses length for pacing. Treat the number as a diagnostic, not a rule: if your readers are experts reading carefully, a 24-word average may be appropriate. For anything people skim on a phone, aim lower.

How to use the Sentence Counter step by step

1. Open the tool and paste your text into Your text.
2. Read Sentences, Paragraphs and Words per sentence in the top row.
3. Check More details for line count, reading time and speaking time.
4. Glance at Most used words for repetition you can trim while you're shortening sentences.
5. Edit directly in the box. The stats refresh as you type, so you can watch the average fall.

Everything runs in your browser; your draft isn't uploaded.

For a total word target, the Word Counter shows the same text with words front and center.

FAQ

Do bullet points count as sentences?

Only if they end with sentence punctuation or are separated by blank lines. A list of short fragments on consecutive lines without periods may be counted as part of one long sentence, which can skew your average upward.

Is a short average always better?

No. An average under 8–10 words often reads as choppy or childish. Aim for variety within a comfortable range rather than the lowest possible number.

Does the counter grade readability like Flesch–Kincaid?

No. It reports sentence and word counts, which are the biggest single input to most readability formulas, but it doesn't calculate a grade level or score syllables.

Paste your next draft into the Sentence Counter and see how long your sentences really are.