What is the INFLESZ scale?

INFLESZ is a Spanish-specific readability scale popularised by Inés Barrio-Cantalejo for evaluating patient information and general text. It reuses the Fernández-Huerta legibility formula and maps the resulting 0-100 score onto five difficulty bands so non-experts can judge whether a document is readable.

How is the score calculated?

The formula is 206.84 minus 0.60 times the average syllables per 100 words minus 1.02 times the average words per sentence. Higher scores mean shorter words and shorter sentences, which read more easily.

What do the bands mean?

Scores above 80 are very easy, 65 to 80 fairly easy, 55 to 65 normal, 40 to 55 somewhat difficult, and below 40 very difficult. Spanish health authorities recommend patient-facing material reach at least the normal or fairly easy band.

How are Spanish syllables counted?

The tool counts vowel groups, treating strong-plus-weak and weak-plus-weak combinations as diphthongs in a single syllable while splitting two strong vowels (hiatus) into separate syllables. It is a heuristic, so rare words may be off by one, but it is accurate enough across a paragraph for the score to be stable.

Spanish INFLESZ Readability Score

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Measure how readable your Spanish text is

English readability formulas like Flesch were tuned on English text and misjudge Spanish, whose words carry more syllables on average. The INFLESZ scale solves this by reusing the Fernández-Huerta legibility formula, which was calibrated for Spanish, and mapping its 0-100 output onto five plain-language difficulty bands. It is the standard tool Spanish health services use to check that patient leaflets and consent forms are actually readable.

How it works

The tool tokenises your text into words and sentences, then estimates syllables by counting vowel groups while respecting Spanish diphthong and hiatus rules. From those counts it computes two inputs: P, the average number of syllables per 100 words, and F, the average number of words per sentence. The INFLESZ score is then:

INFLESZ = 206.84 − (0.60 × P) − (1.02 × F)

A higher score means shorter words and shorter sentences, which read more easily. The result is clamped to 0-100 and mapped onto the five INFLESZ bands.

Tips and example

If your text scores below 55 (somewhat difficult), the two highest-leverage fixes are shortening sentences and swapping long technical terms for everyday words. A sentence of 30 words pushes F up sharply; breaking it into two 15-word sentences lifts the score several points. Replacing a four-syllable clinical term with a two-syllable common word lowers P. Aim for at least the normal band (55-65) for general audiences, and the fairly easy band (65-80) for patient-facing or learner material.