How this instrument works
Sentence case is the capitalization style you were taught in grade school for ordinary prose: the first letter of a sentence is uppercase, and everything else is lowercase except for proper nouns and the word "I". It is the default style of most everyday writing — emails, text messages, form fields — as opposed to Title Case (every word capitalized) or ALL CAPS (every letter capitalized).
This tool applies the mechanical part of that rule. It lowercases the entire input, then finds the first letter of the whole text and the first letter following any . ! or ? that is itself followed by a space, and capitalizes just those letters. That covers the sentence-boundary logic — the part a computer can do reliably from punctuation alone.
What it does not do is re-capitalize proper nouns. Full sentence case also capitalizes names, places, and "I" wherever they appear in a sentence, not just at the start. Telling a proper noun apart from an ordinary word requires a dictionary or language model, not a punctuation rule, so this tool leaves the rest of each sentence in lowercase and expects you to fix proper nouns by hand afterward — the same category of simplification this site already discloses for its title-case tool's minor-word handling.
- Click into the text field and type or paste the text you want converted.
- The sentence-cased result appears immediately below as you type — there is no submit button to press.
- Copy the result directly from the readout, or use the Copy link button to save a permalink that reproduces this exact input.
- Check the result for proper nouns (names, places, "I") and re-capitalize those by hand — this tool only handles sentence-start capitals.
Cleaning up a run-on paragraph with mixed punctuation
Take the input "the quick brown fox. it jumps over the lazy dog! why? because it can." — four sentences, split by a period, an exclamation point, and a question mark, all lowercase to start. The tool returns "The quick brown fox. It jumps over the lazy dog! Why? Because it can." — each sentence's opening letter capitalized, everything else left as typed.
The same rule handles shouty input just as easily. "SOLVETUTOR MATH SOLVER IS OPEN. VISIT US TODAY." is lowercased in full first, then re-capitalized at the two sentence starts only, returning "Solvetutor math solver is open. Visit us today." Notice that no other capital comes back: a proper noun's own capitals — the internal capital T in "SolveTutor", for instance — are not restored anywhere they aren't already a sentence start; that part is left for you to fix by hand.
A single sentence with no closing punctuation at all still works: "one sentence, no ending punctuation" becomes "One sentence, no ending punctuation" — only the very first letter of the text gets capitalized, since there is no . ! or ? to mark a second sentence boundary.
The abbreviation limitation is easy to see in a real sentence: "The recipe needs 2 tbsp. sugar, 1 tsp. salt, and cooks for 45 minutes." comes back as "The recipe needs 2 tbsp. Sugar, 1 tsp. Salt, and cooks for 45 minutes." The tool has no way to tell that "tbsp." and "tsp." are abbreviations rather than sentence endings, so it wrongly capitalizes the ordinary nouns "sugar" and "salt" that follow them, while "45 minutes" at the very end is left alone since no period precedes it there.
Questions
Does this tool capitalize proper nouns and "I"?
No. Full sentence case, as taught in style guides, also capitalizes proper nouns (names, places, brand names) and the pronoun "I" wherever they occur, not just at the start of a sentence. Telling a proper noun apart from an ordinary lowercase word requires a dictionary or language model — something a mechanical punctuation-based transform can't do reliably — so this tool leaves that part to you. Skim the result and re-capitalize any proper nouns by hand.
How does the tool decide where one sentence ends and the next begins?
It looks for a period, exclamation point, or question mark that is immediately followed by whitespace, and treats the next letter after that whitespace as the start of a new sentence. Abbreviations like "Dr." or decimal numbers like "3.5" can trigger a false sentence break this way, since the tool has no way to distinguish a real sentence-ending period from those — that's a known limitation of any purely punctuation-based approach.
Will this fix text that was typed entirely in ALL CAPS?
Yes. The tool always lowercases the entire input first, then capitalizes only the first letter of the text and the first letter after each sentence-ending punctuation mark. So "SOLVETUTOR IS OPEN. VISIT TODAY." and "solvetutor is open. visit today." both produce the identical result: "Solvetutor is open. Visit today."
Is my text sent anywhere when I use this tool?
No. The conversion runs entirely in your browser using JavaScript — nothing you type is sent to a server, logged, or stored anywhere outside your own device (aside from the optional worksheet log, which saves to your browser's local storage only if you choose to keep it).
What's the difference between sentence case and title case?
Sentence case capitalizes only the first letter of each sentence, matching how ordinary prose is written. Title case capitalizes the first letter of every word, which is the style used for headlines and book titles. If you paste a headline into this tool, it will come back looking like a normal sentence rather than a title — use a title-case converter instead if that's what you need.