Sentence Case Converter - Capitalize first letters, restore acronyms

The sentence case converter is a browser-based text tool that capitalizes the first letter of every sentence, lowercases the rest, and restores acronyms such as NASA or PhD, so a pasted draft comes out correctly cased in one click. It is the practical companion for emails, blog posts, transcripts, and APA-style reference lists.

• • Tidy a transcribed draft: Paste raw speech-to-text output and the converter fixes random capitalization and missed full stops.
• • Format APA-style titles: Drop a paper title in to re-case it into sentence case for an APA reference list.
• • Clean chat and forum posts: Run a long all-lowercase or SHOUTING message through the converter before pasting it into a forum or email.
• • Normalize multi-line notes: Paste bullet-free notes where every line is a sentence, and the converter treats each line break as a new sentence start.

The result is a copy-ready Unicode string that pastes into any editor or CMS. Live counts make it easy to verify a transcript has the expected number of sentences.

The acronym preserve list keeps NASA, USA, PhD, AI, and HTML uppercase after the lower-case pass.

For the simpler all-lower case, the Uppercase to Lowercase Converter rewrites every letter in one pass.

The converter reads the input, lower-cases every letter, marks the first letter after every sentence boundary, and upper-cases that letter. Words in the preserve list are then restored to their original case so acronyms survive the lower-case pass.

• text: The pasted string (truncated to 100,000 characters before processing)
• preserveMode: Yes/no toggle that decides whether the preserve list is applied
• preserveList: Comma-separated list of words to restore to their original case (NASA, USA, PhD, AI, etc.)
• stripExtraWhitespace: Yes/no toggle that collapses runs of spaces, trims the ends, and replaces line breaks with spaces

Sentence boundaries are detected on '.', '!', '?', and every newline. The first letter after each boundary is upper-cased; everything else stays lower-case. Lower-casing first is the only way to make ALL CAPS input come out in sentence case.

When the strip-whitespace toggle is on, the converter collapses runs of spaces, trims the ends, and replaces line breaks with a single space, useful for chat-log text.

According to Chicago Manual of Style, section 6.66, the first word of every sentence is always capitalized and proper nouns keep their canonical case, which is the rule the converter applies

According to Unicode Consortium, Latin uppercase letters A-Z sit at U+0041 to U+005A and the matching lowercase letters a-z sit at U+0061 to U+007A

For a simpler all-caps output without sentence boundaries, the Lowercase to Uppercase Converter rewrites every letter in one pass.

Four short ideas cover how the converter works: sentence boundaries, the case map, the preserve list, and the live counts.

The lower-then-recapitalize map mirrors the Unicode case-folding pattern: each letter has one canonical lowercase and one canonical uppercase form, so a lower-case pass is the safest reset.

If the input is just whitespace, every count is zero. Pastes over 100,000 characters are truncated before the stats panel can overflow.

When the live character and word counts are used to plan a fixed-length essay, the Essay Word Count Calculator reports the same word and character totals in a longer-form format.

Four short steps cover the most common workflows, from tidying an all-lowercase email to preparing an APA-style title for a reference list.

1. 1 Paste the draft: Drop the text into the textarea. Up to 100,000 characters fit in one paste.
2. 2 Set the preserve list: Edit the comma-separated preserve list so acronyms and brand names that should stay uppercase (NASA, USA, PhD, iPhone) are in place.
3. 3 Pick the toggles: Choose whether to collapse extra whitespace and whether to keep acronyms uppercase. Both toggles update the result live.
4. 4 Read the counts and copy: Check the source/output character, word, and sentence counts in the result panel, then copy the converted text into your editor, email, or CMS.

A student pastes 'the role of AI in modern research. a phd student writes a literature review. nasa is mentioned.' into the textarea. The converter returns 'The role of AI in modern research. A PhD student writes a literature review. NASA is mentioned.' with AI, PhD, and NASA preserved.

When the same draft is being checked for readability after the sentence-case pass, the Reading Level Calculator reports a Flesch-Kincaid grade level and reading ease score on the same word and sentence counts.

The sentence case converter removes the manual retyping that drags down editing sessions, especially when the source draft is messy or all caps.

• • One-pass capitalization fix: Capitalize the first letter of every sentence in a single pass instead of clicking through a draft.
• • Acronym-safe output: NASA, USA, PhD, AI, and any other word in the preserve list stay uppercase after the lower-case pass.
• • Live character, word, and sentence counts: The result panel tracks source and output characters, words, and sentences side by side for a quick word-count check.
• • Multi-line aware: Treats every line break as a new sentence start, so bullet-free notes and transcript lines come out capped.
• • Runs in the browser: The case map and preserve-list replacement run in JavaScript, so the pasted text never leaves your tab.
• • One-click copy: A copy button on the result panel sends the converted text to your clipboard, ready to paste into the destination editor.

The strongest case for the converter is removing the manual retyping step. A 500-word ALL CAPS transcript can be re-cased in under a second, and the live counts double as a sanity check.

Because the result is a plain Unicode string, it pastes into any editor or CMS without an export step.

When the next step is to style the same source string in a different Unicode form, the Mirror Text Converter applies a separate Unicode-based transform to the same input.

Four short factors decide what the converter returns: sentence boundaries, acronym preservation, whitespace handling, and the source cap.

• • A colon is not a sentence boundary, so 'Note: this is important' is capped only on the N, matching Chicago Manual of Style guidance.
• • The preserve list matches whole words with word boundaries, so 'AI' will not match 'AIM' or 'SAID'. Add the exact form you want to keep uppercase.
• • Sentence detection uses '.', '!', '?'. A decimal like '1.5' is treated as two short sentences; split the number yourself if that matters.

The result is not a full grammar check. The converter only re-cases letters; it does not insert or remove punctuation. If the source draft is missing a period, the next sentence will not be capitalized.

If you need the opposite rule, the title-case workflow lives in a separate tool. Sentence case is the default for prose; title case is the default for headlines.

According to APA Style, titles of works in the reference list and most running text follow sentence case, capitalizing only the first word, the first word after a colon or em dash, and proper nouns

If the destination needs an italic Unicode style on the same source string, the Italic Text Calculator applies a separate Unicode-based styling to the same input.