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English Readability Estimates

Compare six English readability formulas with visible counts and sources. Review word syllables, Fog exclusions and the 30-sentence SMOG sample.

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Inputs that matter
An English passage and optional syllable corrections or Fog exclusions for individual words.
Output to expect
Six formula estimates with their counts and sources, a word pronunciation review and, for longer prose, the selected SMOG sentences.
How it works
English syllables start with a heuristic. Review numbers and abbreviations; corrections apply to every occurrence of the same normalized word. SMOG samples 30 complete sentence candidates.
  • Choose English prose independently of the site language. Non-Latin scripts do not receive these English formula scores.
  • Review the linked Fog exclusions and the actual word and sentence boundaries. Scores estimate surface features, not reader comprehension.
  • Copy includes formulas, sources and your corrections. Editing the source resets corrections and invalidates old export feedback.
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Projects using English Readability Estimates

This tool is part of these guided projects. Each project provides step-by-step instructions with checklists and all the tools you need in one place.

Blog Content Decision Record

Prepare one source-led, rights-cleared, accessible, rendered and owner-approved article package without promising ranking, traffic, publication, or audience response.

6 steps11 toolsStart project

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Operations

Reference & details

How it works

Counts behind the six formulas

W is the number of word-like tokens, S the sentence candidates and Y the estimated spoken syllables. Coleman–Liau uses letters L; ARI uses letters plus digits A. Spaces, punctuation and emoji are excluded from L and A. Scores are displayed to one decimal without clipping.

Pronunciation and Fog review

The syllable 5.0.1 English heuristic supplies initial estimates. Numbers and all-capital abbreviations require spoken counts. A correction applies to all occurrences of a normalized word. Fog starts with 3+ syllable words; inspect the linked procedure and mark exclusions for proper nouns, hyphenated words or applicable -es/-ed endings.

Source: SKC IRB: Gunning Fog procedure

Separate SMOG sample

SMOG requires at least 30 complete sentence candidates. It samples ten near the beginning, ten in the middle and ten near the end, with no overlap. Count repeated words of 3+ syllables each time. The panel lists the selected sentences; Fog exclusions do not affect SMOG.

SMOG estimate = 1.043 × square root of sampled polysyllabic-word occurrences + 3.1291

Source: McLaughlin (1969): SMOG Grading

Flesch Reading Ease

Higher scores usually describe easier surface features. W is counted words, S sentence candidates and Y estimated syllables; very short or unusual prose can produce values outside 0–100.

206.835 − 1.015 × W/S − 84.6 × Y/W

Source: Flesch (1948): A New Readability Yardstick

Flesch–Kincaid grade estimate

This approximate US grade scale uses the same word, sentence and syllable counts. It does not test whether a particular reader understands the passage.

0.39 × W/S + 11.8 × Y/W − 15.59

Source: Kincaid et al. (1975): Navy readability research

Gunning Fog estimate

C counts word occurrences of three or more syllables after the exclusions you review. The denominator remains all counted words.

0.4 × (W/S + 100 × C/W)

Source: SKC IRB: Gunning Fog procedure

Coleman–Liau grade estimate

L counts letters. Digits, spaces, punctuation and emoji are excluded from L; word and sentence boundaries remain estimates.

0.0588 × 100L/W − 0.296 × 100S/W − 15.8

Source: Coleman & Liau (1975): A Computer Readability Formula

Automated Readability Index

A counts letters and digits. Spaces, punctuation and emoji do not increase A. The raw result is shown without an artificial grade-14 ceiling.

4.71 × A/W + 0.5 × W/S − 21.43

Source: Kincaid et al. (1975): Navy readability research

Updated: September 2026

Example Scenarios

Use a tiny passage to inspect the arithmetic rather than infer reader comprehension.

Text: Cat.

→ Flesch Reading Ease 121.2; ARI −6.8; SMOG not calculated.

Enter the phrase and then review NASA as 2 syllables and 12 as 1 syllable.

Text: NASA has 12 people.

→ Before review, pronunciation-dependent formulas wait. With those two corrections, the total is 6 syllables.

Repeat Beautiful people. exactly 30 times, separated by spaces.

Text: Beautiful people. (repeat 30 times)

→ 30 complete sentence candidates and 30 sampled polysyllabic-word occurrences; SMOG estimate 8.8.

FAQ

The formulas here are for English prose. The language control is independent of the site language. Text containing non-Latin scripts is not assigned these English scores; Latin letters alone do not establish that a passage is English. General text counts remain available.

The formula is not mathematically restricted to 0–100. Very short or unusual passages can fall outside that familiar range. The tool preserves the calculated result and shows the counted inputs so you can inspect it.

This implementation follows a 30-sentence sampling procedure. Supply a longer representative passage with at least 30 complete sentence candidates, then inspect the selected groups. Unresolved pronunciations in the sample must also be reviewed.

No. Sentence length, word length and syllables do not measure factual accuracy, organization, a reader’s background knowledge or comprehension. Read the draft in context and use feedback from its intended audience.

Open the word review and enter its spoken syllable count, from 1 to 100. Blank uses the estimate. The correction applies to all occurrences of the normalized word, so inspect words that have different pronunciations in different contexts. Corrections reset when the source text changes.

Paste extracted text or choose a plain text file. Files may use UTF-8, or UTF-16 with an encoding marker. The limit is 2,000,000 file bytes and 500,000 UTF-16 code units after decoding. PDF and Word document parsing is not provided.

Larger inputs run in a browser worker. You can cancel or retry the analysis, or edit the source to replace it. Copy, Print and Project saves wait for a result that matches the current input.

The report names each counting unit and the reading and speaking rates. Where shown, it also includes readability formulas, their counted inputs, word corrections, sources and the selected publishing-length comparison.

About English Readability Estimates

Inspect a draft using six English readability formulas. The panel shows the variables behind each score, keeps raw formula values outside familiar grade ranges and lets you review pronunciation assumptions. These estimates describe surface features of prose.