Pinyin is the official romanization system for Standard Mandarin. It writes Chinese syllables with Latin letters and marks the four tones, so learners and input methods can represent pronunciation without relying only on characters. It is a teaching and typing layer. It is not a second Chinese language, and it is not a Simplified-to-Traditional converter.
This site can add Pinyin to Chinese text and help you type tone marks. The Pinyin Writer turns tone numbers such as hao3 into hǎo. The Chinese to Pinyin converter reads characters and writes marked Pinyin for text or files.
What these tools do
Pinyin tools show pronunciation. They do not convert Simplified characters to Traditional characters. If you need both, convert the characters first with the text or document converter, then generate Pinyin.
Pinyin is also not a translation. zhong1 Guo2 or zhōngguó tells you how 中国 / 中國 is said. It does not explain the word to someone who does not read Chinese. If that is the job you actually have, you need a translator, not a romanizer. See conversion vs translation.
What to read first
- What is Pinyin? — initials, finals, and what the system is for.
- The four tones — contours, neutral tone, and sandhi.
- Tone marks vs tone numbers — mā versus ma1.
- How to type tone marks — operating systems, and when not to bother.
- Add Pinyin to Chinese text — teaching layouts, files, and polyphones.
If you already know the theory and only need output, skip to the Chinese to Pinyin converter.
Limits in one paragraph
Libraries guess polyphones. Names need a person. Citation tones may not match spoken sandhi. PDFs must contain real text. Those limits are why the articles above exist: so a generated line of Pinyin is a draft you know how to check, not a finished linguistic analysis.