Enter some pinyin with tone numbers in the input box (e.g. "Ni3 hao3 ma") and it should be automatically converted to tone marks as you type.
You can change the pinyin with tone marks back to pinyin with numbers (or Bopomofo) by selecting options from the drop-down menu and then pressing the "Convert" button.
Once you select an option from the drop-down menu, conversion should be instantaneous (i.e. as-you-type).
Try cutting and pasting pinyin into the box and watch it convert on the fly!
You can also use this converter to type Hanyu Pinyin and output Bopomofo (using the option Convert Numbers to Bopomofo), or vice versa.
This converter uses JavaScript and does not require an internet connection. You can download a copy of the converter here and use it offline in your browser.
Examples
Numbers to Tone Marks: Han4zi4 biao1yin1 zhen1 hao3wan2! → Hànzì biāoyīn zhēn hǎowán!
Tone Marks to Numbers: Hànzì biāoyīn zhēn hǎowán! → Han4zi4 biao1yin1 zhen1 hao3wan2!
