What is a sentence case converter?
A sentence case converter is a text tool that formats writing the way standard prose is capitalized: the first letter of each sentence is capitalized, and every other letter is lowercased — turning "HELLO world. how ARE you?" into "Hello world. How are you?" This one runs entirely as JavaScript inside your browser, so there's no upload and no server round-trip: your text never leaves your device. The conversion updates live as you type or paste.
How the conversion works
The tool first lowercases the entire input, then capitalizes the very first letter of the text and any letter that immediately follows a period, exclamation point or question mark plus a space. This matches how sentence case works in word processors like Microsoft Word. Because the rule relies on punctuation, unusual formatting — like abbreviations ("Dr.", "e.g.") or decimal numbers ("3.14") — can occasionally trigger an unwanted capital letter, so it's worth a quick read-through afterward.
What sentence case doesn't fix
Sentence case only handles the first letter of each sentence — it doesn't know which words are proper nouns. Names, place names, brand names, and the pronoun "I" won't be automatically re-capitalized if they land mid-sentence, so you may need to manually fix those after converting. This is expected behavior, since true proper-noun detection requires understanding meaning, not just punctuation.
Common uses for sentence case
- Cleaning up pasted text — fix text copied from a source that was in all caps or randomly capitalized.
- Standardizing headlines — many modern style guides (including AP-adjacent web style) prefer sentence case over Title Case for headings.
- Form & database entries — normalize inconsistently capitalized user-submitted data.
- UI copy — buttons, labels and menu items in modern app design commonly use sentence case rather than Title Case.
- Email & message drafts — quickly fix text that was accidentally typed with caps lock on.
Case style comparison
| Case style | Example | Common use |
|---|---|---|
| Sentence case | Hello world. How are you? | Body text, headings, UI copy, standard prose |
| UPPERCASE | HELLO WORLD | Headers, warnings, acronyms, constants |
| lowercase | hello world | Usernames, URLs, minimalist branding |
| Title Case | Hello World | Headlines, book & movie titles |
| aLtErNaTiNg cAsE | hElLo WoRlD | Memes, playful social captions |