Alternate Readability Formulas (SMOG / Coleman-Liau / Gunning Fog / ARI)
Four additional reading-grade formulas beyond Flesch-Kincaid: SMOG (McLaughlin 1969), Coleman-Liau (1975), Gunning Fog (1952), and ARI (Smith + Senter 1967). Same text input as Y.1.
Formula and source
SMOG = 1.043 * sqrt(polysyllables * (30/sentences)) + 3.1291. Coleman-Liau = 0.0588 * L - 0.296 * S - 15.8 (L = letters/100 words; S = sentences/100 words). Gunning Fog = 0.4 * (words/sentences + 100 * complex/words). ARI = 4.71 * (chars/words) + 0.5 * (words/sentences) - 21.43.
SMOG per McLaughlin, 'SMOG Grading: A New Readability Formula,' Journal of Reading 12:8 (1969). Coleman-Liau per Coleman + Liau, 'A computer readability formula designed for machine scoring,' Journal of Applied Psychology 60:2 (1975). Gunning Fog per Gunning, 'The Technique of Clear Writing' (1952). ARI per Smith + Senter, 'Automated Readability Index,' AMRL-TR-66-220 (1967), public-domain federal publication.
Audience
This tile is built for trades and the adjacent professions in the Educators and K-12 group. The interactive calculator runs entirely in your browser. No account, no fee, no advertising, no tracking.
Related tools
Posture
Rough Logic answers the math question the working professional asks on the job. The site is a calm, fast, ad-free, account-free, ever-free reference. It does not interpret code. It does not replace the licensed professional. It does not store your inputs. The Authority Having Jurisdiction governs all installations and inspections.