Sentence Case Converter
Quickly convert your text into proper sentence case — the first letter of each sentence is capitalized and the rest are lowercase. Ideal for essays, emails, social media posts, and any writing that needs clean, readable formatting. No signup, no uploads — just paste, tweak, and copy.
Why use this Sentence Case Converter?
Manually fixing capitalization across a long text is tedious and error‑prone. Our tool instantly applies sentence case rules — capitalizing after periods, question marks, and exclamation points — while optionally keeping ALL CAPS words intact. It's perfect for cleaning up messy drafts, formatting social media captions, or making sure your email sounds professional. Because everything runs in your browser, your text stays 100% private.
- Smart sentence detection – recognizes . ! ? and newlines as sentence boundaries.
- Preserve intentional uppercase – toggle to keep words like "NASA" or "OK" in all caps.
- Instant preview – the output updates as you type, so you see the result immediately.
- Lightweight & private – no server calls, no data ever leaves your device.
How to convert to sentence case (step‑by‑step)
1. Paste your text
Copy any text — a paragraph, a list of sentences, or even a full article — and drop it into the left box.
2. Tweak options
Decide if you want to keep acronyms in all caps, ensure the first letter of each sentence is capitalized, or treat newlines as sentence boundaries.
3. See the result
The sentence‑case version appears instantly on the right. Toggle the options to see how the output changes in real time.
4. Copy or download
Click Copy to grab the formatted text, or Download to save it as a .txt file. Then paste it wherever you need it.
Example: before and after
| Input text | Sentence case output |
|---|---|
| hello world. this is a TEST. another sentence? YES! NASA is great. | Hello world. This is a test. Another sentence? Yes! NASA is great. |
Common use cases
- Essays & assignments: Quickly fix accidental all‑caps or all‑lowercase paragraphs before submission.
- Email drafts: Make sure your message starts with a capital letter and ends with proper punctuation.
- Social media posts: Turn a hastily typed caption into properly capitalized sentences.
- Transcription: Clean up transcribed speech where capitalization is missing or inconsistent.
- Code comments: Format documentation strings that need proper sentence case.
Pro tips
- The tool recognizes common sentence‑ending punctuation: period (.), question mark (?), and exclamation point (!).
- Enable "Preserve ALL CAPS words" to avoid turning acronyms like "NASA" or "FBI" into lowercase. The tool checks if a word is fully uppercase before deciding to lowercase it.
- If your text has bullet points or line‑by‑line sentences, enable "Treat newlines as sentence boundaries" to capitalize the start of each line.
- For full control over case, check out our other tools: Case Converter (uppercase, lowercase, title case) and Title Case Converter.