Change your default font size before you start composing

The fastest way to set a default font size in Outlook is to change it in your message settings before you write anything. Open Outlook and go to File > Options > Mail. Under the "Compose messages" section, click Stationery and Fonts. A window will open with tabs for "Personal Stationery," "New Mail Message," and "Replying or Forwarding." Click the New Mail Message tab, then click the Font button. Choose your size from the dropdown — most people find 11 or 12 points readable without strain — and click OK twice to save.

This method works in Outlook 2019, Outlook 2021, and Outlook for Microsoft 365 on Windows. The setting applies to every new message you write going forward, but not to messages you have already composed. If you use Outlook on Mac, the process is slightly different: go to Outlook > Preferences > Composing, then find the font size option in the message formatting area.

Key Takeaways

  • Default font size in Outlook is set through File > Options > Mail > Stationery and Fonts > New Mail Message tab.
  • The change applies only to new messages you write, not to replies or forwarded messages unless you adjust those tabs separately.
  • Font size 11 or 12 points is standard for business email and readable on most screens without zooming.
  • If you use Outlook on Mac, the setting is in Preferences > Composing instead of the Windows menu path.

Set a different size for replies and forwarded messages

Outlook lets you set a separate default font size for messages you reply to or forward. This is useful if you want new messages in a larger size but prefer to match the original message size when responding. In the same Stationery and Fonts window, click the Replying or Forwarding tab, then click Font and choose your preferred size. Click OK to save.

Some people use this to keep replies at the original sender's font size for consistency, while making their own new messages larger for readability. You can also set different fonts entirely — for example, a sans-serif font for new messages and a serif font for replies — though most workplaces expect consistency across all your outgoing mail.

Adjust font size in the compose window if you need it temporarily

If you want to change the font size for just one message, you do not need to alter your default settings. Open a new message, select all the text with Ctrl+A (or Command+A on Mac), then use the font size dropdown in the toolbar. The toolbar appears at the top of the compose window and shows a box with a number — that is your font size selector. Click it and choose a new size.

This one-time change does not affect your default. When you close the message and write a new one, it will revert to whatever default you set in Options. This method is handy when you need larger text for a specific recipient or when you are pasting content that came in at an awkward size.

Check your theme and display settings if text still looks too small

Sometimes the issue is not Outlook's font size but your Windows or Mac display scaling. If you have set Outlook to 12 points but the text still appears tiny, check your system settings. On Windows, go to Settings > System > Display and look at the "Scale and layout" section — if it is set below 100%, text across all programs will appear smaller. Increasing it to 125% or 150% makes everything larger without changing Outlook's actual font size.

On Mac, go to System Preferences > Displays and check the resolution setting. Choosing "Larger Text" will scale everything on your screen. You can also zoom in within Outlook itself by pressing Ctrl and scrolling your mouse wheel up (or Command and scrolling on Mac), though this is a temporary fix that resets when you close the program.

Use styles or templates if you change fonts frequently

If you regularly switch between different font sizes for different types of messages — large for clients, smaller for internal notes — consider creating message templates. In Outlook, go to File > New > Message, format it the way you want, then go to File > Save As and choose Outlook Template as the file type. Give it a name like "Client Email" or "Internal Memo" and save it.

Later, when you want to use that template, go to File > New > Choose a Template and select the one you saved. The message will open with your preset font size, font type, and any signature or formatting you included. This is faster than changing your default settings back and forth, and it keeps your messages consistent within each category.

Outlook web and mobile apps have limited font size control

If you use Outlook on the web (outlook.office.com) or the Outlook mobile app, you cannot set a default font size the way you can in the desktop version. The web version uses your browser's zoom level — press Ctrl and the plus key to zoom in, or use your browser's settings menu. The mobile app (iOS and Android) does not offer font size settings at all; it uses the system font size from your phone or tablet.

For the mobile app, go to your device's accessibility settings to increase text size globally. On iPhone, that is Settings > Accessibility > Display & Text Size > Larger Accessibility Sizes. On Android, it is Settings > Accessibility > Text and display > Font size. These changes affect all apps on your device, not just Outlook.

Frequently Asked Questions

Does changing the default font size affect emails I have already sent?

No. Your default font size setting only applies to new messages you write after you change it. Emails already in your sent folder keep whatever size they were when you sent them. Recipients also see the size you sent, not your current default.

Why does my reply look like a different size than my new message?

You may have set different defaults for new messages and replies. Check File > Options > Mail > Stationery and Fonts and look at both the "New Mail Message" and "Replying or Forwarding" tabs. They can have different font sizes. If you want them to match, set them both to the same size.

Can I set a default font size for specific contacts?

Outlook does not have a built-in feature to set font size per contact. Your best option is to use templates for different groups — one template for clients, one for colleagues, one for vendors — and choose the right template when you start a message to that person.

What font size should I use for business email?

11 or 12 points is standard for business email. It is readable on most screens without zooming and looks professional. Anything smaller than 10 points can be hard to read, especially for people with vision challenges. Anything larger than 14 points can look informal or like you are shouting.