Typing fractions and subscripts in LibreOffice Writer

LibreOffice Writer does not automatically convert typed fractions like "1/2" into the single-character fraction symbol ½. You have three ways to insert them: use the Insert menu to pick from built-in fraction characters, type the code and let AutoCorrect convert it, or manually format numbers as subscript. Which method you choose depends on whether you want a true fraction character (smaller, single glyph) or subscript formatting (smaller text positioned below the baseline).

The fastest route for common fractions is AutoCorrect. Type the fraction code — for example, type 1/2 and press Space or Enter, and LibreOffice converts it to ½ automatically. This works for 1/2, 1/4, 3/4, and a few others. For fractions outside that set, or if AutoCorrect is off, you will need the Insert menu or manual subscript formatting.

Key Takeaways

  • AutoCorrect converts common fractions like 1/2, 1/4, and 3/4 into single-character symbols when you press Space or Enter after typing them.
  • The Insert > Special Character menu lets you search for and insert any fraction character by name, even uncommon ones like 1/8 or 5/6.
  • Manual subscript formatting (Ctrl+Shift+B on Windows, Cmd+Shift+B on Mac) makes the denominator smaller and lower, but does not create a true fraction character.
  • AutoCorrect settings can be turned on or off in Tools > AutoCorrect Options > Localized Options, where you control which fractions convert automatically.

Using AutoCorrect to convert typed fractions

When AutoCorrect is on (the default in most LibreOffice installations), typing a fraction code and then pressing Space, Tab, or Enter triggers the conversion. The most common fractions that convert this way are 1/2 (½), 1/4 (¼), 3/4 (¾), 1/3 (⅓), and 2/3 (⅔). Type the numerator, a forward slash, the denominator, then press Space or Enter. LibreOffice replaces the three characters with a single fraction glyph.

If the fraction does not convert, AutoCorrect may be off, or the fraction you typed is not in the built-in list. Check by going to Tools > AutoCorrect Options, then click the Localized Options tab. Look for the checkbox labeled something like "Replace 1/2 with ½" or "Fractions". If it is unchecked, click it to turn AutoCorrect fractions back on. If it is already checked and your fraction still did not convert, that fraction code is not in the AutoCorrect table — use the Insert menu instead.

Inserting fractions from the Special Character menu

For fractions not covered by AutoCorrect, or if you prefer to choose the character yourself, use Insert > Special Character. A dialog box opens showing a grid of characters. In the search field at the top, type the fraction you want — for example, type "one eighth" or "1/8" and LibreOffice filters the grid to show matching characters. Click the fraction you want, then click Insert.

If searching by name does not work, try the Subset dropdown. Select Latin-1 Supplement or Number Forms to narrow the character set. Scroll through the grid until you see the fraction you need. Once you find it, double-click it to insert it at your cursor, or single-click and then click the Insert button. The dialog stays open so you can insert multiple fractions without closing and reopening it.

Formatting text as subscript instead of using fraction characters

Subscript formatting makes text smaller and positions it below the baseline of regular text. This is different from a true fraction character — it does not create a single glyph, and the result looks like two separate pieces of text rather than one unified symbol. However, subscript works for any number or letter, not just fractions, and it is useful when you need to format chemical formulas, footnote markers, or mathematical notation.

To apply subscript formatting, select the text you want to make subscript (usually just the denominator), then press Ctrl+Shift+B on Windows or Cmd+Shift+B on Mac. The selected text shrinks and drops below the line. To remove subscript, select the text again and press the same key combination. You can also go to Format > Text > Subscript from the menu, though the keyboard shortcut is faster.

Turning AutoCorrect fractions on or off

If AutoCorrect fractions are converting when you do not want them to, or if you want to turn them back on, go to Tools > AutoCorrect Options. Click the Localized Options tab. Look for a checkbox with text like "Replace 1/2 with ½" or simply "Fractions". Uncheck it to stop automatic conversion, or check it to turn it back on. Click OK to save your choice.

You can also customize which fractions convert by going to Tools > AutoCorrect Options > Replace tab. This tab shows a table of all the text-to-character replacements LibreOffice knows about. Search for "1/2" or other fractions in the list. If you want to remove a fraction from the AutoCorrect table, select it and click Delete. If you want to add a custom fraction conversion, type the code in the "Replace" field, the character in the "With" field, and click New.

Choosing between fraction characters and subscript formatting

A true fraction character (½, ¼, ⅜) is a single glyph in the font, so it prints and displays cleanly at any size. It is the right choice when you are writing text that mentions a measurement or quantity — "Add 1/2 cup of flour" looks professional with the fraction character. Subscript formatting is the right choice when you are writing mathematical or scientific notation where the denominator needs to be clearly separate from surrounding text, or when you need a fraction that does not have a built-in character.

Keep in mind that not all fonts include all fraction characters. If you insert a fraction character and it does not display or prints as a box, the font you are using does not have that glyph. Switch to a different font (like Liberation Serif or DejaVu Sans) that includes more fraction characters, or use subscript formatting instead, which works in any font.

Frequently Asked Questions

Why did my 1/2 not convert to a fraction symbol?

AutoCorrect fractions may be turned off. Go to Tools > AutoCorrect Options > Localized Options and check the "Fractions" or "Replace 1/2 with ½" checkbox. Also, AutoCorrect only converts when you press Space, Tab, or Enter after typing the fraction — if you just type it and move on without pressing a key, it will not convert.

Can I create a fraction that is not in the built-in list?

Yes, using subscript formatting. Select the denominator, press Ctrl+Shift+B (Windows) or Cmd+Shift+B (Mac), and it becomes subscript. You can also add a custom AutoCorrect entry: go to Tools > AutoCorrect Options > Replace, type your fraction code in "Replace", insert the character in "With", and click New.

What is the difference between a fraction character and subscript?

A fraction character like ½ is a single symbol in the font, so it looks unified and prints cleanly. Subscript is formatting applied to regular text, making it smaller and lower — it looks like two separate pieces. Fraction characters are better for text; subscript is better for math notation or when you need flexibility with any numbers.

Does LibreOffice convert fractions in all languages?

AutoCorrect fractions depend on your language setting and which fractions are in the AutoCorrect table for that language. English includes 1/2, 1/4, 3/4, 1/3, and 2/3. Other languages may have different sets. You can always use Insert > Special Character to find any fraction regardless of language.