Flesch-Kincaid Calculator

Calculate Flesch Reading Ease Score (FRES) and Flesch-Kincaid Grade Level (FKGL) for any text. Includes target audience matching, average sentence length, syllables per word, and benchmark comparisons.

Flesch Reading Ease Score
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Flesch-Kincaid Grade Level —
Target Audience —
Extended More scenarios, charts & detailed breakdown ▾
Flesch Reading Ease (0–100)
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Equivalent Grade —
Avg Sentence Length (words) —
Avg Syllables per Word —
Professional Full parameters & maximum detail ▾

Readability Scores

Flesch Reading Ease (FRES) —
FK Grade Level (FKGL) —
Target Audience —

Text Statistics

Avg Sentence Length (words) —
Avg Syllables / Word —
Word Count —
Sentence Count —

Benchmark

Benchmark Comparison —

How to Use This Calculator

  1. Paste your text into the Input Text field (at least 3 sentences for reliable results).
  2. Read the Flesch Reading Ease Score (0–100, higher = easier).
  3. Read the FK Grade Level (US school grade required to understand the text).
  4. Use the Audience Match tab to check if your text matches a specific audience.
  5. Use the Professional tier for a full breakdown with benchmarks.

Formula

Flesch Reading Ease: 206.835 − (1.015 × ASL) − (84.6 × ASW)
FK Grade Level: (0.39 × ASL) + (11.8 × ASW) − 15.59
Where ASL = average sentence length (words), ASW = average syllables per word.

Example

Example: "The cat sat on the mat. The dog ran fast." → ASL = 5.0, ASW ≈ 1.1 → FRES ≈ 91.6 (Very Easy, 5th grade) | FKGL ≈ 1.1 (1st grade reading level).

Frequently Asked Questions

  • The Flesch Reading Ease Score (FRES) rates text on a 0–100 scale. Higher scores mean easier reading. Scores 90–100 are very easy (5th grade). Scores 60–70 are standard (8th–9th grade). Scores below 30 are very difficult (college graduate level). The formula was published by Rudolf Flesch in 1948.
  • The Flesch-Kincaid Grade Level (FKGL) converts the Reading Ease Score to a US school grade level. A score of 8.0 means an 8th-grader can understand the text. Developed by J. Peter Kincaid for the US Navy in 1975 to assess the readability of technical manuals.
  • For general public content (websites, consumer products, news), aim for 60–70. For marketing copy and simple instructions, target 70–80. Academic writing is typically 30–50. Legal documents often score below 30. The Plain Language movement recommends 60+ for all government communications.
  • The formula counts syllables by counting vowel clusters in each word. One or two consecutive vowels count as one syllable. Common exceptions: silent "e" endings and "-ed" endings are often not counted. The calculation is an approximation — manual syllable counting may differ slightly.
  • FK Reading Ease and Grade Level use average sentence length and average syllables per word. SMOG focuses specifically on polysyllabic words (3+ syllables) and is preferred for healthcare. Gunning Fog counts "complex" words (3+ syllables). Each formula has different strengths — FK is the most widely used and integrated in tools like Microsoft Word.

Related Calculators

📖 SMOG Readability Calculator 📖 Readability Calculator 🎤 Speech Time Calculator 📊 Word Frequency Counter
Sources & References (5) ▾
  1. Flesch (1948) — A New Readability Yardstick — Journal of Applied Psychology / Rudolf Flesch
  2. Kincaid et al. (1975) — Derivation of New Readability Formulas — US Navy Personnel Research & Development Center
  3. Microsoft Office Readability Statistics — Microsoft
  4. Hemingway Editor Methodology — Hemingway App
  5. Plain English Campaign — Language Research — Plain English Campaign