Metrics Explained
Understanding the readability metrics and scores used by Claru
What are Readability Metrics ?
We test how hard your original Document is to read. We also test if after Conversion. We use special Tests that look at things like:
- How long your Sentences are
- How hard your Words are
- How many Syllables Words have
We use 5 different Tests. Each Test checks different things. This helps us make sure your Easy Read Document is really easy to read.
Want to Check Your Document's Readability ?
Use our Free Online Readability Checker to test your Document before converting it. Get all 5 Metrics instantly — just enter your email to get started.
Try Free Readability CheckerFlesch Reading Ease Score
What it does: This Test shows how easy your Text is to read.
How it works: It looks at how long your Sentences are and how many Syllables your Words have.
The Scores: You get a Score from 0 to 100. Higher Scores mean easier to read.
Why we use it: This Test has been used since the 1940s. Governments and Schools use it all over the World.
UK Reading Levels:
- 90-100 Very Easy (Primary School)
- 80-89 Easy (Year 6-7 level)
- 70-79 Fairly Easy (Year 8-9 level)
- 60-69 Standard (GCSE level)
- 50-59 Fairly Difficult (A-Level)
- 30-49 Difficult (University level)
- 0-29 Very Difficult (Postgraduate level)
Flesch-Kincaid Grade Level (Reading Level)
What it does: This Test tells you what School Year you need to be in to understand the Text.
How it works: It looks at Sentence Length and Syllables to work out Difficulty.
The Scores: Lower School Years mean easier to read.
Why we use it: The US Navy created this Test in the 1970s. We changed it to use UK School Years instead of American Grades.
UK School Year Equivalents:
- Reception/Year 1: Ages 4-6
- Years 2-6: Ages 7-11 (Primary)
- Years 7-9: Ages 12-14 (Secondary)
- Years 10-11: Ages 15-16 (GCSE)
- Years 12-13: Ages 17-18 (A-Level)
- University: Ages 18-22
- Postgraduate: 22+ years
Dale-Chall Readability Score
What it does: This test looks for hard words that people might not know.
How it works: It has a list of 3,000 easy words that most Year 4 children know. If your text uses words not on this list, they are "difficult" words.
The scores: You get a score from 0 to 10. Lower scores mean easier to read.
Why we use it: This test is better at finding difficult words than just counting syllables. It knows which words people actually find hard.
Score Interpretation:
- 4.9 or below Year 4 and below
- 5.0-5.9 Years 5-6
- 6.0-6.9 Years 7-8
- 7.0-7.9 Years 9-10
- 8.0-8.9 Years 11-12
- 9.0-9.9 Year 13 (Sixth Form)
- 10.0+ University level
Gunning Fog Index
What it does: This test finds long words and long sentences that make reading hard.
How it works: It counts words with 3 or more syllables. These are "complex" words.
The scores: Lower school year scores mean easier to read.
Why we use it: A newspaper publisher called Robert Gunning made this test in 1952. It is good at finding writing that is harder than it needs to be.
Target Levels:
- 6-8: Easy to read
- 9-12: Acceptable for general public
- 13-16: Difficult - university level
- 17+: Very difficult - postgraduate
• Newspapers: 8-11
• Popular magazines: 10-13
• Government documents: Should be 12 or less
Automated Readability Index (ARI)
What it does: This test counts letters in words instead of syllables.
How it works: It looks at how many letters are in your words and how long your sentences are.
The scores: Lower school year scores mean easier to read.
Why we use it: The US Air Force made this test in 1967. It is faster for computers to use because it counts letters, not syllables.
What makes it different:
- Does not count syllables
- Works well with technical writing
- Works the same in different languages
- Easy for computers to use
Easy Score: how easy your Document is to read
The Easy Score puts all the tests below into one number, out of 100. A higher number means an easier read. It shows how much easier your Document is than the one you gave us. Easy Read and Plain English have their own yardsticks, because they have different goals. Both aim for 80 or more, which is the level of human-made Easy Read.
It looks at 4 things, and each is worth a quarter:
- Sentence length: Words per sentence, and how many sentences are over 15 words.
- Word length: Reading Age, Flesch Reading Ease, Gunning Fog and ARI.
- Familiar words: Dale-Chall, and how many hard words are not on our Easy Read word list.
- Plain structure: How many sentences use the passive voice, ALL CAPS, brackets, or several ideas at once. Research on health information (Godsmark and Reading, 1996) found these make writing harder to read, and ordinary formulas miss them.
A very weak group limits the whole score. It can be at most 30 points above your weakest group, so hard words cannot be hidden by tidy punctuation.
| Score | What it means |
|---|---|
| 80 to 100 | Very Easy to read |
| 65 to 79 | Fairly Easy to read |
| 45 to 64 | Quite hard to read |
| 0 to 44 | Hard to read |
Why We Use Multiple Metrics
Each test is good at different things:
- Flesch Reading Ease: Most people know this test
- Flesch-Kincaid: Tells you the school year needed
- Dale-Chall: Finds words people do not know
- Gunning Fog: Finds sentences that are too long
- ARI: Easy for computers to use
Using all 5 tests together gives us:
- Better answers
- We can find different problems
- We can check our work
- We know our Easy Read version is better
- Professional results
Easy Read Target Scores
For good Easy Read documents, Claru tries to get these scores:
Flesch Reading Ease
Easy to Very Easy
School Year Level
Age 11 and under
Sentence Length
Short and clear
Related Guides
Free Readability Checker
Check any document or website — see all these metrics in action.
Try Free ToolText Difficulty Highlighter
See which sentences are hard to read, highlighted sentence by sentence.
Try Free ToolGetting the Best Results
Prepare your documents well before conversion for the clearest Easy Read output.
Read Guide