9 formulas · free calculators
Readability formulas, explained
Every readability formula measures something slightly different - some count syllables, others count characters or compare your words against a list of familiar ones. Each page below explains one formula, shows its equation, and gives you a calculator to run your own text through.
Flesch Reading Ease
The classic 0-100 ease score - higher means easier to read.
Flesch-Kincaid Grade Level
Translates readability into a US school grade level.
Gunning Fog Index
Estimates years of education needed, weighting complex words.
SMOG Index
Grade estimate from polysyllabic word density - a health-literacy standard.
Coleman-Liau Index
Grade level from characters per word instead of syllables.
Automated Readability Index
Character-based grade score, built for automated processing.
Linsear Write
Developed for the US Air Force to grade technical manuals.
FORCAST
Made for forms and lists - no full sentences required.
New Dale-Chall
Compares text against 3,000 words familiar to young readers.
Which formula should you use?
For general writing, Flesch Reading Ease and Flesch-Kincaid Grade Level are the most widely recognised - they are the scores built into word processors and cited in style guides.
For health and safety material, SMOG is the usual standard. For forms and lists that lack full sentences, use FORCAST. And when you care whether your vocabulary is genuinely familiar rather than merely short, New Dale-Chall compares each word against a list of 3,000 words known to young readers.
Rather than pick one, the main analyzer runs all nine at once and gives you a consensus grade level.