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Sentence Case Converter

Rewrite text so only sentence starts and proper nouns are capitalised.

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Quick Tool Overview

The Sentence Case Converter rewrites text so that only sentence openings are capitalised — the way ordinary prose is written, and now the house style for headings and interface text at most design systems. Acronyms, the pronoun "I" and any names you protect are left intact.

What it does
Capitalises sentence starts and lowercases the rest
You give it
A heading, paragraph or document in the wrong case
You get back
Clean sentence-case text with acronyms preserved
Best for
Headings, UI labels and rescuing all-caps text
Text Tools Free, unlimited use No sign-up Runs in your browser

About the Sentence Case Converter

Sentence case is how ordinary prose is written: a capital letter at the start of each sentence, and nowhere else except proper nouns. It is also, increasingly, the house style for headings, buttons and interface labels, because it reads faster than title case and is far harder to get wrong.

The hard part of doing this automatically is knowing what to leave alone. A naive converter lowercases NASA, turns "I" into "i" and mangles names. This one keeps recognised acronyms in capitals, always restores the pronoun "I", recognises sentence boundaries properly — a full stop in "Dr." or "3.5" does not start a new sentence — and can be given a list of proper nouns to protect.

Key features of the Sentence Case Converter

Real sentence detection

A full stop inside "Dr." or "3.5" does not start a new sentence, so abbreviations and decimals no longer create stray capitals.

Acronyms protected

NASA, HTML and PDF keep their capitals instead of being flattened by the lowercase pass.

The pronoun "I" restored

Including in contractions such as "I've" and "I'll" — the most common artefact of a plain lowercase conversion.

Your own protected words

Add proper nouns and product names so they survive exactly as written.

Line-by-line option

Treat each line as its own sentence, which is what a bulleted list or a set of headings needs.

How to use the Sentence Case Converter

  1. 1

    Paste your text

    A heading, a paragraph or a document typed in the wrong case.

  2. 2

    Set what to protect

    Acronyms and the pronoun "I" are preserved by default; add any names you also want left alone.

  3. 3

    Read the result

    Each sentence starts with a capital and everything else is lowercased.

  4. 4

    Copy it back

    Copy the converted text, or send it back to the input box for another pass.

Frequently asked questions

It looks for a full stop, question mark or exclamation mark followed by whitespace, but ignores full stops inside abbreviations such as "Dr." and "e.g." and inside decimal numbers such as 3.5, which would otherwise create false sentence breaks.

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