Twitter/X does not count every character equally. Japanese, Chinese, and Korean characters are each worth two units against the 280-unit limit, so a Japanese post that looks short can hit the cap fast. This tool applies the real weighting rules so you know exactly how much room you have left.
How it works
The platform’s twitter-text library defines code-point ranges that weigh two
units; everything else weighs one. The counter walks your text code point by code
point and applies:
weight 2 → CJK ideographs, hiragana, katakana, Hangul,
full-width forms, CJK symbols/punctuation, emoji
weight 1 → Latin letters, digits, ASCII punctuation,
spaces, line breaks
limit → 280 weighted units
Summing the weights gives the figure the platform itself would compute. A purely Japanese post therefore reaches 280 at about 140 characters.
Example and tips
The greeting こんにちは is 5 characters but weighs 10 units. Mixing in Latin
helps: OK!またね is 6 characters but 11 units, since the two ASCII letters in
OK weigh 1 each while the rest weigh 2. If you need to trim, swapping a
full-width exclamation ! for a half-width ! saves one unit each time.