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Readability Score Calculator

Check the reading level of your writing using Flesch Reading Ease, Flesch-Kincaid, Gunning Fog, SMOG, Coleman-Liau and the Automated Readability Index.

What this tool does

Check the reading level of your writing using Flesch Reading Ease, Flesch-Kincaid, Gunning Fog, SMOG, Coleman-Liau and the Automated Readability Index. You fill in these fields: Text. It shows flesch Reading Ease, flesch-Kincaid grade, gunning Fog index, SMOG grade, coleman-Liau index, automated Readability Index, words, sentences, syllables (estimated), and words of 3 or more syllables.

Inputs

  • Text: Longer text, up to 100000 characters.

How to use

  1. Type the text.
  2. Read the result: flesch Reading Ease, flesch-Kincaid grade, gunning Fog index, SMOG grade, coleman-Liau index, automated Readability Index, words, sentences, syllables (estimated), and words of 3 or more syllables. It appears once every required field has a valid value.

Worked examples

Example 1. Inputs:

  • Text: "The cat sat on the mat."

Results:

  • Flesch Reading Ease: 116.1 (Very easy)
  • Flesch-Kincaid grade: -1.4
  • Gunning Fog index: 2.4
  • SMOG grade: 3.1
  • Coleman-Liau index: -4.1
  • Automated Readability Index: -5.1
  • Words: 6
  • Sentences: 1
  • Syllables (estimated): 6
  • Words of 3 or more syllables: 0
  • Note: SMOG was designed for samples of 30 sentences. This text has 1, so the SMOG grade is an extrapolation.

How this is worked out: 6 words, 1 sentence, every word one syllable (6 syllables), 17 letters (3+3+3+2+3+3), no word of 3+ syllables. Flesch = 206.835 - 1.015 x 6 - 84.6 x 1 = 116.145. FK = 0.39 x 6 + 11.8 x 1 - 15.59 = -1.45. Fog = 0.4 x 6 = 2.4. SMOG = 1.043 x sqrt(0) + 3.1291 = 3.1291. CL: L = 17/6 x 100 = 283.333, S = 1/6 x 100 = 16.667, 0.0588 x 283.333 - 0.296 x 16.667 - 15.8 = 16.66 - 4.9333 - 15.8 = -4.0733. ARI = 4.71 x 17/6 + 0.5 x 6 - 21.43 = 13.345 + 3 - 21.43 = -5.085.

Example 2. Inputs:

  • Text: "Beautiful butterflies fly. Nobody can understand it!"

Results:

  • Flesch Reading Ease: 9.9 (Very difficult)
  • Flesch-Kincaid grade: 12.7
  • Gunning Fog index: 24.3
  • SMOG grade: 11.2
  • Coleman-Liau index: 12.7
  • Automated Readability Index: 9.9
  • Words: 7
  • Sentences: 2
  • Syllables (estimated): 16
  • Words of 3 or more syllables: 4
  • Note: SMOG was designed for samples of 30 sentences. This text has 2, so the SMOG grade is an extrapolation.

How this is worked out: 7 words, 2 sentences (a full stop and an exclamation mark). Syllables by the tool's spelling rule (each run of one or two vowel letters is a syllable): beautiful 4 (ea, u, i, u; speech has 3, which shows the count is an estimate), butterflies 3 (u, e, ie), fly 1, nobody 3 (o, o, y), can 1, understand 3 (u, e, a), it 1 = 16; 4 words have 3+ syllables, and all 4 are Gunning complex words (butterflies still has 3 without its -es). 44 letters (9+11+3+6+3+10+2). Flesch = 206.835 - 1.015 x 3.5 - 84.6 x 16/7 = 206.835 - 3.5525 - 193.3714 = 9.9111. FK = 0.39 x 3.5 + 11.8 x 16/7 - 15.59 = 1.365 + 26.9714 - 15.59 = 12.7464. Fog = 0.4 x (3.5 + 100 x 4/7) = 0.4 x 60.6429 = 24.2571. SMOG = 1.043 x sqrt(4 x 30/2) + 3.1291 = 1.043 x 7.74597 + 3.1291 = 11.2081. CL: L = 44/7 x 100 = 628.571, S = 2/7 x 100 = 28.571, 0.0588 x 628.571 - 0.296 x 28.571 - 15.8 = 36.96 - 8.4571 - 15.8 = 12.7029. ARI = 4.71 x 44/7 + 0.5 x 3.5 - 21.43 = 29.6057 + 1.75 - 21.43 = 9.9257.

Example 3. Inputs:

  • Text: "Café au lait Très bon."

Results:

  • Flesch Reading Ease: 119.7 (Very easy)
  • Flesch-Kincaid grade: -2.8
  • Gunning Fog index: 1.0
  • SMOG grade: 3.1
  • Coleman-Liau index: -7.6
  • Automated Readability Index: -4.2
  • Words: 5
  • Sentences: 2
  • Syllables (estimated): 5
  • Words of 3 or more syllables: 0
  • Note: SMOG was designed for samples of 30 sentences. This text has 2, so the SMOG grade is an extrapolation.

How this is worked out: Words: Café, au, lait, Très, bon = 5 (the doubled space adds none). The text has a blank line after 'lait'. A line break ends a sentence, so 'Café au lait' and 'Très bon.' make 2. The spelling rule is built for English: it drops the accents and counts each of these words as 1 syllable (5 in all), although café is spoken with 2. Letters: 4+2+4+4+3 = 17, counting é and è as letters. Flesch = 206.835 - 1.015 x 2.5 - 84.6 = 119.6975. FK = 0.39 x 2.5 + 11.8 - 15.59 = -2.815. Fog = 0.4 x 2.5 = 1. SMOG = 3.1291. CL: L = 17/5 x 100 = 340, S = 2/5 x 100 = 40, 0.0588 x 340 - 0.296 x 40 - 15.8 = 19.992 - 11.84 - 15.8 = -7.648. ARI = 4.71 x 3.4 + 0.5 x 2.5 - 21.43 = 16.014 + 1.25 - 21.43 = -4.166.

Example 4. Inputs:

  • Text: "Dr. Smith saw 12 tests happening. They walked home, e.g. slowly."

Results:

  • Flesch Reading Ease: 93.6 (Very easy)
  • Flesch-Kincaid grade: 1.6
  • Gunning Fog index: 2.2
  • SMOG grade: 7.2
  • Coleman-Liau index: 3.4
  • Automated Readability Index: 1.9
  • Words: 11
  • Sentences: 2
  • Syllables (estimated): 14
  • Words of 3 or more syllables: 1
  • Note: SMOG was designed for samples of 30 sentences. This text has 2, so the SMOG grade is an extrapolation.

How this is worked out: Words: Dr, Smith, saw, 12, tests, happening, They, walked, home, e.g, slowly = 11. Sentences: the stop after Dr is a title and the last stop of 'e.g.' is followed by a lower case word, so neither ends a sentence; the stops after 'happening' and 'slowly' do, giving 2. Syllables by the spelling rule: happening 3 (a, e, i), slowly 2 (o, y), walked 1 (final -ed dropped), home 1 (silent e), the number 12 counts as 1, the other six 1 each = 14. One word has 3+ syllables (happening), but it is not a Gunning complex word because it has 2 without -ing. Letters: 2+5+3+5+9+4+6+4+2+6 = 46, and 48 with the digits of 12. Flesch = 206.835 - 1.015 x 5.5 - 84.6 x 14/11 = 206.835 - 5.5825 - 107.6727 = 93.5798. FK = 0.39 x 5.5 + 11.8 x 14/11 - 15.59 = 2.145 + 15.0182 - 15.59 = 1.5732. Fog = 0.4 x (5.5 + 0) = 2.2. SMOG = 1.043 x sqrt(1 x 30/2) + 3.1291 = 1.043 x 3.87298 + 3.1291 = 7.1686. CL (letters only): L = 46/11 x 100 = 418.182, S = 2/11 x 100 = 18.182, 0.0588 x 418.182 - 0.296 x 18.182 - 15.8 = 24.5891 - 5.3818 - 15.8 = 3.4073. ARI (letters and digits): 4.71 x 48/11 + 0.5 x 5.5 - 21.43 = 20.5527 + 2.75 - 21.43 = 1.8727.

Limitations

  • The formulas were designed for English prose. Other languages and lists give unreliable scores.
  • Syllable counts are estimates from spelling and are wrong for some words, so the four scores that use them can differ a little from a count made by ear.
  • Gunning's exclusion of proper nouns and compound words is not applied, so the Fog index can read a little high.
  • Sentence ends are found by punctuation and line breaks. Initials and most abbreviations are counted as sentence ends, which makes sentences look shorter and the text easier.
  • Very short texts give extreme scores, including negative grades and Reading Ease above 100.
  • The scores measure sentence and word length only. They do not judge clarity, accuracy or style.

FAQs

Q: Which formulas does it use?
A: Flesch Reading Ease (1948), Flesch-Kincaid grade (1975), Gunning Fog (1952), SMOG (1969), Coleman-Liau (1975) and the Automated Readability Index (1967). The grade scores are US school grades.
Q: What do the words under the Reading Ease score mean?
A: They name the band the score falls in: 90 or more is very easy, 80 to 90 easy, 70 to 80 fairly easy, 60 to 70 standard, 50 to 60 fairly difficult, 30 to 50 difficult and below 30 very difficult. A higher score means easier text.
Q: Why do the scores differ from each other?
A: Each formula weighs sentence length, word length and long words differently, so they rarely agree exactly. Compare them as a group rather than trusting one.
Q: Are the syllable counts exact?
A: No. Syllables are estimated from spelling, so some words are miscounted. That affects Flesch, Flesch-Kincaid, Gunning Fog and SMOG, but not Coleman-Liau, which counts letters, or the Automated Readability Index, which counts letters and digits.
Q: How are words counted?
A: A word is any run of characters between spaces that holds a letter or digit. A hyphenated word, a word with an apostrophe and a number each count as one word, and a number counts as one syllable.
Q: How are sentences counted?
A: A sentence ends at a full stop, question mark or exclamation mark followed by a space, or at a line break, so a heading on its own line counts as one. A full stop does not end a sentence after a common title such as Dr. or Mr., or when the next word starts with a lower case letter. Initials and other abbreviations before a capital letter are counted as sentence ends.
Q: Why does SMOG show a note about 30 sentences?
A: SMOG was built on samples of 30 sentences. With fewer, the grade is an extrapolation and is less reliable.

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