Gunning Fog Index & SMOG Readability Grade Level Calculator

Compute Fog = 0.4 × (Words/Sentences + 100 × ComplexWords/Words) and SMOG grade.

Gunning Fog Readability Index
12.02 grade level
SMOG Readability Grade 11.4 grade
Complex Word Percentage (≥3 Syl) 11 %
Words per Sentence 19.05 words/sent
Inputs
words
Total words in text sample.
sentences
Total sentences in text sample.
complex words
Words with 3 or more syllables (excluding proper nouns & common suffixes).
Results & Graph
Gunning Fog Readability Index
12.02 grade level
SMOG Readability Grade
11.4 grade
Complex Word Percentage (≥3 Syl)
11 %
Words per Sentence
19.05 words/sent

Gunning Fog Readability Index

Graph 1 • Total Words Sensitivity Recalculates the domain equation across 50% to 150% of the primary input while holding other parameters constant.
0 grade level 7.8 grade level 15.5 grade level 50%: 12.61 grade level 12.6 50% 75%: 11.58 grade level 11.6 75% 100%: 12.02 grade level 12.0 100% 125%: 13.04 grade level 13.0 125% 150%: 14.36 grade level 14.4 150%
Graph 2 • Primary & Supporting Metric Comparison Compares the primary output alongside supporting domain benchmarks.
Gunning Fog Readability Index 12.02 grade level SMOG Readability Grade 11.4 grade Complex Word Percentage (≥3 Syl) 11 % Words per Sentence 19.05 words/sent
Graph 3 • Exact Output Table & Units Displays each calculated output in its exact domain unit.
Gunning Fog Readability Index12.02 grade levelSMOG Readability Grade11.4 gradeComplex Word Percentage (≥3 Syl)11 %Words per Sentence19.05 words/sent
Summary: With 11% complex words and 19 words/sentence, Gunning Fog Index is 12.02 and SMOG grade is 11.4.
Summary: With 11% complex words and 19 words/sentence, Gunning Fog Index is 12.02 and SMOG grade is 11.4.
⚡ Send result to: GPA & Grade →Date Difference →Time Card & Time Zone →
Interactive chart & math engine powered by CalculatorGraph

Formula & Mathematical Methodology: Gunning Fog & SMOG Formula

GunningFog = 0.4 × [ (Words / Sentences) + 100 × (ComplexWords / Words) ]
GunningFog = 0.4 × [ (Words / Sentences) + 100 × (ComplexWords / Words) ]
  • totalWords: Total Words (words)
  • totalSentences: Total Sentences (sentences)
  • complexPolysyllabicWords: Complex Polysyllabic Words (complex words)

Rounding: Standardized test and time rules follow official scoring rubrics; continuous outputs round to 2 decimal places.

Worked Example: Benchmark Scenario: Gunning Fog & SMOG

Compute Fog = 0.4 × (Words/Sentences + 100 × ComplexWords/Words) and SMOG grade.

  1. Enter your raw test counts, credit hours, or schedule parameters.
  2. Evaluate the formula: GunningFog = 0.4 × [ (Words / Sentences) + 100 × (ComplexWords / Words) ].
  3. Inspect the primary score/duration, supporting metrics, and 3 SVG graphs.
Result: Computes Gunning Fog & SMOG via GunningFog = 0.4 × [ (Words / Sentences) + 100 × (ComplexWords / Words) ].

Frequently Asked Questions

How does the Gunning Fog Index & SMOG Readability Grade Level Calculator calculate results?

It evaluates GunningFog = 0.4 × [ (Words / Sentences) + 100 × (ComplexWords / Words) ] directly in your browser and updates three custom SVG visualizations in real time.

Can I use Goal Seek to find the exact score or hours I need?

Yes. Click "🎯 Goal Seek" in the results toolbar to solve backwards for any input variable.

Are my academic or schedule inputs kept private?

Yes. All calculations run 100% locally in your browser.

Education · Writing, Research & Psychometrics

Gunning Fog Index & SMOG Readability Grade Level Calculator: inputs, method, and how to read the result

Compute Fog = 0.4 × (Words/Sentences + 100 × ComplexWords/Words) and SMOG grade.

Choose inputs for the case you are checking

The defaults are illustrative. Replace them with values for your case and keep the units shown beside each field.

  • Total Words: Total words in text sample.
  • Total Sentences: Total sentences in text sample.
  • Complex Polysyllabic Words: Words with 3 or more syllables (excluding proper nouns & common suffixes).

What the calculation includes

With the default values shown, Gunning Fog Readability Index is 12.02 grade level. The calculation follows Gunning Fog & SMOG Formula; the formula and variable definitions above show how the inputs combine.

One-input check: With the other defaults held constant, changing Total Words from 800 words to 880 words changes Gunning Fog Readability Index from 12.02 grade level to 12.38 grade level. This is a comparison inside the calculator's stated model, not a prediction.

Where to use caution

  • Uses official published scoring scales, Carnegie unit conventions, and ISO calendar rules.
  • Official standardized test equating curves vary slightly by test form administration date.

Scope: Global Academic, Psychometric & ISO 8601 Time Standard Check the assumptions and limitations against your situation before relying on the estimate.

More in Education: GPA & Final Grade Calculator, Date Difference & Business Days Calculator, Time Duration, Shift Time Card, Overtime Pay & Time Zone Calculator.