In 1993, Spanish journalist Pedro Szigriszt Pazos created a tool that changed how we measure Spanish text. The Flesch-Szigriszt Index uses math to predict if people will understand your content or give up after the first paragraph.
What is it?
It’s a Spanish version of the famous Flesch Reading Ease Score. But it’s not just a translation. Szigriszt adjusted the formula specifically for how Spanish works. This makes it the best tool for measuring if Spanish content is easy to read.
The formula
Flesch-Szigriszt Index = 206.835 − (62.3 × syllables/words) − (words/sentences)
How the formula works
The Flesch-Szigriszt Index formula measures two simple things:
1. Do you use long or short words?
It counts how many syllables each word has on average.
- “House” = 1 syllable
- “Refrigerator” = 5 syllables
More syllables = harder to read.
2. Do you write long or short sentences?
It counts how many words each sentence has on average.
- “We sell cars” = 3 words
- “We offer state-of-the-art automotive vehicles” = 6 words
More words per sentence = harder to read.
How it calculates
You start with 206 points (the maximum). Then:
- Points are subtracted for using long words (many syllables)
- Points are subtracted for using long sentences (many words)
The result
- Easy text: close to 100 points (not many deducted)
- Hard text: close to 0 points (almost all deducted)
In short: The shorter your words and sentences, the higher your score and the easier your text is to read.
What this measures:
- Syllables per word: How many syllables your words have on average
- Words per sentence: How long your sentences are
How to read your score
The index gives you a score from 0 to 100. In 2008, researcher Inés María Barrio Cantalejo created the INFLESZ Scale with five levels:
| Score | Difficulty Level | Who Can Read It |
|---|---|---|
| <40 | Very Hard | Scientific papers, philosophy. Needs college education. |
| 40-55 | Hard | Specialized texts. Needs high school or college level. |
| 55-65 | Normal | Average reader can understand. This is the key threshold. |
| 65-80 | Pretty Easy | School textbooks, general magazines. |
| >80 | Very Easy | Even teenagers can understand. |
The 55-point line: Success or failure
Research shows that texts scoring below 55 are much less likely to be read and understood. This is especially true for health info, education, and business content. If your website, sales pitch, or teaching materials score below 55, you’re losing money.
Why your business should care
1. SEO impact
Google doesn’t just count keywords. It watches what users do. If someone lands on your site and leaves after 10 seconds because they can’t understand it, your bounce rate goes up and your ranking goes down. A low Flesch-Szigriszt score means your content isn’t working for real users.
2. Customer costs
If your website doesn’t clearly explain what problem you solve, you’ll spend more on ads to make up for it. A score above 55 makes your sales process work better. Less explaining. Fewer objections. More sales.
3. Looking professional
Many people think complex writing makes them look smart. The opposite is true. Studies show that scientific journals average 37.9 points, while popular magazines (read by millions) score 60 points. Do you want to reach experts or customers who buy?
Real examples
Healthcare
The Flesch-Szigriszt Index is now standard for checking medicine labels and patient forms. The results are bad. Most of these documents score “Hard” (40-55) when they should be above 55 for people to actually understand them.
Education
School textbooks in Spain average 67.39 points (Pretty Easy). That’s why they work. But many private schools write their websites with scores below 50. This creates a wall that keeps people out.
Marketing
Companies that make their landing pages score above 60 see better sales numbers. The reason is simple. When customers quickly understand the value, they’re more likely to buy.
How to improve your score
Simple steps
- Shorten your sentences. Each extra word per sentence lowers your score. Aim for 12 to 17 words per sentence.
- Use simpler words. Change “implement synergistic methodologies” to “use methods that work together.” Same idea. Fewer syllables.
- Cut the jargon. If customers search for “tutoring for kids,” don’t offer “cognitive-behavioral pedagogical reinforcement.”
- Break up paragraphs. Big blocks of text scare people away. Split ideas into small chunks.
Tools to measure it
You don’t need to count syllables by hand. Try these:
- INFLESZ Program: Free at www.legibilidad.com (old but works)
- Legible.es: Free online tool that checks multiple readability scores
- SpanishReadability.com: Made specifically for Spanish text
- Screaming Frog SEO Spider: For checking entire websites at once
The big mistake: Thinking complex = professional
Top companies learned decades ago that clarity sells. Complexity scares people away. Apple doesn’t use tech talk to explain products. They use phrases a teenager can understand. This isn’t luck. It’s strategy.
If your company brags about its “disruptive cross-functional solution ecosystem,” you’re losing customers. If instead you say “we help companies grow faster,” you’re making sales.
The data
The INFLESZ Scale study looked at 210 Spanish publications:
- Scientific journals: 37.9 average score (Hard)
- Popular magazines: 60 points (Normal)
- School textbooks: 67.39 points (Pretty Easy)
Conclusion: Content that reaches more people is simpler, not more complex.
Other readability tools
Other formulas exist for Spanish readability:
- Fernández-Huerta: Earlier version of Flesch for Spanish, less tested than Szigriszt
- SOL Formula: Based on syllables per 100 words
- Crawford: Adapted from English, less accurate for Spanish
But the Flesch-Szigriszt Index with the INFLESZ Scale is the standard in Spanish-speaking countries, especially in Spain and Latin America.
Common questions
Should I always aim for above 55?
It depends on your audience. If you’re writing for academics or specialists, a score of 40-50 might be okay. But if you want to sell, teach the general public, or rank on Google, you need above 55. For business websites, aim for 60-70.
Does a high score mean my content is shallow?
No. Clear doesn’t mean simple. Einstein could explain relativity in ways people understood. Deep ideas and easy reading aren’t opposites. They work together when done right.
What about technical or legal content?
Even in technical or legal documents, clarity helps understanding and prevents mistakes. Medicine labels in Spain are legally required to be understandable, but many still fail. Clarity doesn’t remove technical accuracy. It makes it accessible.
Bottom line
The Flesch-Szigriszt Index isn’t just academic trivia. It predicts behavior. It tells you if your text will be read or abandoned. If your message will be understood or ignored. If your content investment will pay off or disappear into high bounce rates.
In a world where attention is scarce, clear writing isn’t optional. It’s the difference between being found and being ignored. Between selling and wondering why you’re not selling. Between leading your industry and chasing competitors.
The question isn’t whether your content is readable. The question is: can you afford for it not to be?