Sentence Case Converter

The Sentence Case Converter rewrites your text in proper sentence case, lowercasing the body of every sentence and capitalising only the first letter after each full stop, question mark, or exclamation mark. It is the quickest way to tidy up text that arrived in all caps, all lowercase, or an inconsistent mixture of the two.

It is ideal for cleaning up pasted content, fixing headings that were typed with Caps Lock on, and normalising user-generated text before publishing it. Rather than retyping a paragraph or correcting each sentence by hand, you paste the text and get a consistently capitalised version that reads naturally and looks professional.

The converter detects sentence boundaries using terminal punctuation and line breaks, and it also capitalises the standalone word I so contractions and pronouns read correctly. An optional setting preserves acronyms such as NASA or HTML so they are not flattened to lowercase, and because everything runs locally in your browser, your text is never uploaded.

Features

• Lowercases the whole text and capitalises the first letter of every sentence automatically.
• Detects sentence boundaries after full stops, question marks, exclamation marks, and line breaks.
• Capitalises the standalone pronoun I so contractions and sentences read correctly.
• Offers an option to preserve acronyms like NASA, HTML, or PDF instead of lowercasing them.
• Updates the result live as you edit the text or toggle the acronym option.
• Handles multi-paragraph text, keeping each paragraph's first sentence capitalised.
• Runs instantly and privately with no account, no upload, and no size limit.

How to use Sentence Case Converter

1. Paste or type the text you want to convert into the input box.
2. Enable Preserve acronyms if your text contains initialisms you want to keep uppercase.
3. The sentence-cased result appears instantly in the output area.
4. Review the statistics panel to see how many sentences were capitalised.
5. Edit the text further if needed and watch the output update live.
6. Copy the cleaned text or export it as a TXT file for later use.

Benefits

• Turns all-caps or all-lowercase content into clean, readable sentence case in one step.
• Saves time when normalising pasted or user-generated text before publishing.
• Keeps acronyms intact when the preserve option is enabled, avoiding awkward lowercasing.
• Handles multiple paragraphs so long passages are cleaned consistently throughout.
• Processes private drafts safely because nothing leaves your browser.
• Gives instant feedback on how many sentences were adjusted for quick verification.

Sentence case is the standard style for body text, and getting it right by hand is tedious when content arrives in the wrong case. This converter first lowercases everything to establish a clean baseline, then restores capitalisation at each sentence start, which produces reliable results even when the original text mixed cases unpredictably.

Sentence detection relies on punctuation, so unusual formatting, abbreviations ending in a full stop, or missing punctuation can occasionally shift where a new sentence is recognised. When you need to keep the existing letters exactly as they are and only fix the leading capital, the Capitalize Each Sentence tool is a gentler option, while the acronym-preserving setting here helps whenever technical terms would otherwise be lowercased.