Readability checker
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Paste your writing and this marks the sentences that are long enough to lose a reader, in the text itself, with the word count on each one. Sentence length is the strongest single predictor of how hard something is to read, and unlike a score it points somewhere you can do something about. It works on Thai as well as English, which most readability tools do not: Thai is written without spaces between words, so anything that counts spaces reports nonsense on it.
Paste some writing. The sentences that are too long get marked in the text, with their length on each one.
Flesch reading ease, from 1948, and the grade level derived from it. Above 60 is comfortable for a general audience. It counts English syllables, so it appears only for text in the Latin alphabet.
Your text, with the long sentences marked
over 25 words over 35 words
Frequently asked questions
Is my text sent anywhere?
No. It is measured in this tab as you type, and never leaves the browser. The site’s security policy sets connect-src ‘none’, so the browser blocks network requests from these pages, so nothing could be sent even if the code tried. That matters more here than on most tools, because the thing being checked is usually a draft.
Why is there no readability score for Thai?
Because there is no Thai formula that anybody agrees on, and inventing one would be inventing authority. English has Flesch: sixty years old, tested against real comprehension, and reproducible, so two tools that implement it agree with each other. Nothing comparable exists for Thai. Producing a number anyway and calling it a Thai reading score would let people make decisions with something that has no evidence behind it, which is worse than saying plainly that there is none.
So what does it measure in Thai?
Sentence length, which is the strongest single predictor of difficulty in every language it has been studied in, and which needs no formula to be useful. It also points at the specific runs that are too long, which is something a writer can act on this afternoon. A score tells you that something is wrong somewhere; a marked sentence tells you where.
How does it find where a Thai sentence ends?
By the spaces. Thai has no full stop, and the space is what does that job: it separates one thought from the next in the way a comma and a full stop do in English. The standard text-segmentation library refuses to split Thai into sentences at all and returns the whole passage as one, which is correct and useless, so this measures the runs between spaces instead. A Thai text written with no spaces at all comes back as a single very long run, and that is a real finding about the writing rather than a limitation here.
How are Thai words counted with no spaces between them?
With the Thai dictionary that ships inside your browser, through the standard segmentation interface. It is the same data your phone uses to decide where to break a line of Thai text. Without it a tool has to ship a dictionary of its own or count characters and pretend they are words, and the second one is what most of them do.
Where do 25 and 35 words come from?
From plain-language guidance rather than from a law. Most style guides for public writing put the target average somewhere between 15 and 20 words, and treat anything past 25 as a sentence to look at again. Past about 35 a reader has to hold too much in their head to reach the end on one pass. They are lines for drawing attention, not thresholds anybody passes or fails.
Is a low score a reason to rewrite something?
Not on its own. These measurements are about form, not meaning: a short sentence can be baffling and a long one can be perfectly clear if it is well built. What the marking is genuinely good at is finding the sentence you wrote at the end of a long day, which has three ideas in it and no full stop, and which you cannot see any more because you know what it was meant to say.