What Gunning Fog score is ideal?

A Fog index of 8 is ideal for most public communication. Values below 8 are easy; 8–12 acceptable; 12–17 difficult; above 17 very difficult. Most bestselling novels score 6–8; legal documents often exceed 20.

What counts as a complex word in Gunning Fog?

A complex word is any word with 3 or more syllables, with exceptions for proper nouns, compound words formed from short words (e.g., 'bookkeeper'), and verbs made 3 syllables by adding -ed or -es.

Gunning Fog Index Readability Calculator

Calculate the Gunning Fog index GFI = 0.4 × (words/sentences + 100 × complex words/words), where complex words have 3+ syllables. Returns estimated years of formal education required to understand the text on first reading.

Data set — comma or newline separated

Statistical Results — n = 8

Count (n)8

Sum (Σx)40

Min2

Max9

Range7

Q14

Q35.5

IQR1.5

Mean (μ)5

Median4.5

Mode4

Pop. Variance (σ²)4

Pop. Std Dev (σ)2

Sample Variance (s²)4.571428571

Sample Std Dev (s)2.138089935

Skewness0.65625

Excess Kurtosis-0.21875

How to Use

Enter the values for the scenario you are assessing. Calculate the Gunning Fog index GFI = 0.4 × (words/sentences + 100 × complex words/words), where complex words have 3+ syllables. Returns estimated years of formal education required to understand the text on first reading. Use the gunning fog index result to inform your calculation.

Gunning Fog Index Readability Calculator

How to Use

Frequently Asked Questions

What Gunning Fog score is ideal?

What counts as a complex word in Gunning Fog?