Hanyu Pinyin is the standard romanisation of Mandarin Chinese, and its four tones are written either with a number after the syllable (ma1, ma4) or with a diacritic over a vowel (mā, mà). This free tool converts between the two notations in both directions, applying the official tone-mark placement rule, instantly and with no upload.
How it works
To add accents, the tool reads each syllable and its trailing tone number (1 to 4, with 5 or 0 meaning neutral). It then places the mark on the correct vowel using the standard rule: if the syllable contains an a or e, the mark goes there; in the combination ou it goes on the o; otherwise it goes on the last vowel. Each base vowel (a, e, i, o, u, ü) has four pre-composed accented forms for the four tones, so the chosen vowel is simply swapped for its toned version.
To remove accents, the tool detects any accented vowel in a syllable, records which tone it represents, replaces it with the plain vowel, and appends the matching number after the syllable. Neutral-tone syllables are returned with no number.
Tips and notes
Because keyboards lack the ü key, type v or ue where ü is needed — for example lv4 or lue4 yields lǜ. Tone marks always sit on vowels, never consonants, which is why the placement rule matters for clusters like iao or uan. Words and punctuation between syllables pass through unchanged. Everything runs locally in your browser — your text is never sent to a server.