Readability score — Flesch, SMOG, Coleman-Liau in one analysis

The five readability scores in one glance

Each formula approximates the same property — how hard text is to read — using different proxies. Here’s when each is most useful:

• Flesch Reading Ease (0–100, higher = easier) — the most quoted score. Best for marketing and consumer content. Sample interpretation: 90–100 (5th grade), 60–70 (standard), 30–50 (college), 0–30 (graduate).
• Flesch-Kincaid Grade Level— same inputs as Flesch, but outputs a US grade. Best for matching content to an audience age.
• SMOG Index— built specifically for health and medical content. Counts polysyllabic words rather than estimating syllable totals. Generally the most conservative (highest grade level).
• Coleman-Liau Index— uses character count rather than syllables. Best for technical text, code-adjacent content, or any text where syllable estimation breaks.
• Automated Readability Index (ARI)— similar inputs to Coleman-Liau. Originally calibrated for typewritten text; today serves as a sanity-check on Coleman-Liau.

How to read your aggregate score

We compute the average grade level across all formulas. This smooths out quirks (one formula getting fooled by an outlier sentence) and gives a more stable estimate. As a rule:

• Average grade 6–8: very accessible. Good for marketing copy, landing pages, popular blog posts.
• Average grade 8–10: standard. The reading level of major newspapers and most successful blogs.
• Average grade 10–12: professional. B2B content, long-form journalism, non-fiction books.
• Average grade 12–15: specialist. Academic papers, technical documentation, research writing.
• Average grade 15+: dense. Most readers struggle. Check whether you really need this level.

How to improve a low readability score

If your Flesch Reading Ease is below 50 (or grade level above 12) and that’s higher than you want, here’s the playbook:

• Identify the longest sentence in your text. Almost always it can become two clearer sentences.
• Scan for 4+ syllable words. Each one you swap for a shorter word raises your Flesch Ease by 0.5–1 point.
• Cut filler phrases: “in order to,” “due to the fact that,” “at this point in time.”
• Convert passive voiceto active where natural. “The decision was made by the team” → “The team decided.”