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Readability
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Paste text above to see sentence length, kanji ratio and which sentences run long.
A checker that instantly quantifies how readable a piece of Japanese text is. Paste an article, report, email, manuscript or blog post and it counts the characters, the number of sentences, the average length per sentence and the length of the longest sentence, then shows the proportion of kanji, hiragana, katakana, Latin letters/digits and symbols as bar charts. Readability in Japanese hinges largely on keeping each sentence from getting too long and not packing in too many kanji. This tool lists every sentence over a threshold (default 60 characters), longest first, so you can see exactly which sentences to split in two. A kanji ratio of around 30% is generally considered easy to read — too low feels overly casual, too high feels stiff — and the tool comments on where your text sits relative to that guide. Use it to polish press releases, review internal or official documents, rewrite blog posts, or tune a manuscript for readability. Your text is never sent to a server — all analysis happens entirely on your device.
How to use
- Paste the text whose readability you want to check (article, email, report, etc.).
- See the character count, sentence count, average sentence length and longest sentence, plus the kanji / hiragana / katakana mix.
- Sentences over the long-sentence threshold are listed longest first. Split long sentences in two, and if the kanji ratio is high, open some words into kana.
FAQ
Is my text sent to a server?
No. All analysis runs inside your browser. The text you enter is not uploaded, stored, or transmitted; it is handled only on your device, so it's safe even for confidential documents or personal drafts.
What kanji ratio is considered readable?
As a rule of thumb, text reads comfortably when kanji make up around 30% of the characters. Below about 20% it can feel casual or childish, while well above 40% it tends to feel stiff and dense. The tool comments on where your text sits relative to this guide — it isn't an absolute rule, since the ideal varies with your audience and the type of document.
How is sentence length measured?
Sentences are split on terminators (。！？ and ASCII !?) and line breaks, and each sentence's length is its character count (code points) excluding whitespace. Average sentence length is total non-space characters divided by the number of sentences. Overly long sentences make it hard to track subject and predicate, so use this to find sentences worth splitting.
Can I change the long-sentence threshold?
Yes. Use the "Long-sentence threshold" box in the toolbar to set anything from 20 to 400 characters (default 60). A readable Japanese sentence is often cited as roughly 40–60 characters, but the right length depends on the document, so adjust to your purpose. Your setting is remembered next time.
Does it work for English text?
The character count, sentence count, average length and long-sentence detection all work for English too. However, the kanji and kana ratios are Japanese-specific metrics, so English-only text will show a high Latin/digit share. For fine-grained English difficulty, a syllable-based readability score is a better fit.