Sentence Case Converter
Turn shouting capitals or broken casing back into readable prose. Runs entirely in your browser.
What sentence case does
Sentence case is the ordinary casing of written English: one capital at the start of each sentence, and everything else lower case unless it is a proper noun. It is what body copy, form fields, product descriptions and support articles should be written in, and it is what text pasted out of a spreadsheet or a PDF very often is not.
The conversion runs in two passes. First the whole line is lowered, which is the only way to undo text that arrived in full capitals. Then capitals are restored at the start of the text, after every full stop, question mark and exclamation mark, and after every line break, so a pasted list keeps each item capitalised.
The pronoun problem, and how it is handled
Lowering the line also lowers the English pronoun I, which would be wrong in every sentence it appears in. It is restored afterwards, and so are the contractions, so I'm, I'll, I've and I'd come back correctly rather than needing a manual pass.
Proper nouns are the honest limit
No converter can tell that march is a month rather than a verb, or that bill is a name rather than an invoice, without understanding the sentence. If your text is full of names, switch on Keep words already in capitals before converting: anything written in full capitals is then preserved, which protects acronyms such as NASA, HTML and PDF. Mixed-case proper nouns still need a read-through, and that is worth knowing before you paste a thousand words in.
Examples
| Typed | Sentence case |
|---|---|
| HELLO WORLD. THIS IS A TEST! | Hello world. This is a test! |
| and i am here. so are you | And I am here. So are you |
| first line second line | First line Second line |
| ANNUAL REPORT FOR MARCH 2026 | Annual report for march 2026 |
The last row shows the proper-noun limit honestly: march is lowered because nothing in the line marks it as a month. That one is quicker to fix by hand than to guess at automatically.
How to use it
Paste into the upper box and the converted text appears underneath as you type. Copy result puts it on the clipboard, Download .txt saves it as a file, and Use result as input moves the output back up so you can keep working on it. The counts along the bottom track characters, words, sentences, lines and reading time as you go.
Questions
How does the tool know where a sentence ends?
It capitalises the first letter of the text, the first letter after a full stop, question mark or exclamation mark followed by a space, and the first letter after a line break. That covers ordinary prose. An abbreviation such as e.g. mid-sentence can trigger a capital, which is the one case worth checking by eye.
Will it lower-case my name or my acronyms?
By default yes, because sentence case has to lower the line before it can rebuild it and it has no way to know that a word is a proper noun. Switch on Keep words already in capitals and anything written in full capitals, such as NASA or HTML, is preserved.
Does it fix the pronoun I?
Yes. Lower-casing the line would turn the English pronoun I into i, so it is restored afterwards, including the contractions I'm, I'll, I've and I'd.
What is the difference between this and the Case Converter?
This tool does one job, sentence case, and gives it options of its own. The Case Converter offers seven styles including upper, lower, title, capitalized, alternating and inverse. Use this one for body copy and that one when you want to compare styles.
Is my text uploaded anywhere?
No. The conversion runs inside your browser and this tool has no backend, so nothing you paste is transmitted, logged or stored.
Related: Title Case Converter for headlines and Word Counter for length checks. Everything else is on the all tools page.
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