Change your default font size in Outlook through the Settings menu

The fastest way to change the default font size in Outlook is through the app's settings. Open Outlook, go to File > Options (on Windows) or Outlook > Preferences (on Mac), then find the mail formatting section. From there you can set a new default font size that applies to all new messages you compose.

The exact location depends on which version of Outlook you use — the desktop app, Outlook on the web, or Outlook for Mac each have slightly different menu paths. But the principle is the same: you're telling Outlook what size to use when you start typing a fresh email, rather than changing the size of emails you've already received.

Key Takeaways

  • Windows Outlook users find font settings under File > Options > Mail > Composing Messages.
  • Mac Outlook users go to Outlook > Preferences > Composing Messages to set a new default size.
  • Outlook on the web requires you to open a new message, click the formatting menu, and change the size before composing — there is no global default setting.
  • Changing the default font size only affects new messages you write, not messages you receive or have already sent.
  • If you use multiple email accounts in Outlook, the default font size applies to all of them unless you change it again.

Windows Outlook: Setting the default font size

In Outlook on Windows, open the app and click File in the top left corner. Select Options from the menu that appears. In the Options window, click Mail on the left side, then look for the section labeled Composing Messages.

Under Composing Messages, you'll see a button that says Stationery and Fonts. Click that button. A new window opens with tabs at the top — make sure you're on the Personal Stationery tab. You'll see a section for New Mail Messages with a dropdown or button labeled Font. Click it to open the font dialog, where you can select your font and, more importantly, choose the size from the Size dropdown. Pick the size you want (common options are 10, 11, 12, and 14 point), then click OK twice to save your changes.

Mac Outlook: Setting the default font size

On Mac, the path is slightly different. Open Outlook and click Outlook in the menu bar at the very top of the screen. Select Preferences from the dropdown. In the Preferences window, find and click Composing Messages.

Look for the section labeled Composing and Editing or Message Format. You should see options for font and size. Click the font dropdown or the size dropdown to change the default. Once you've selected a new size, close the Preferences window — your changes save automatically on Mac.

Outlook on the web: Changing font size for each message

Outlook on the web (the version you access through a browser at outlook.com or through your organization's web portal) does not have a global default font size setting. Instead, you set the size each time you compose a message. Click New Message to start writing an email.

In the compose window, look for the formatting toolbar. You'll see a button with an A and a dropdown arrow next to it — this is the font size control. Click the dropdown to see size options (usually 8 through 28 point), select the size you want, and then type your message. The size you choose applies only to that one message. If you want a different size for your next email, you'll need to change it again.

What happens when you change the default font size

When you set a new default font size, it applies only to new messages you compose from that point forward. Emails you've already sent keep their original formatting. Emails you receive from other people are not affected — they display in whatever size the sender chose, and your default setting does not override that.

If you use multiple email accounts in the same Outlook installation, the default font size you set applies to all of them. If you later want a different size for one account, you'll need to go back into settings and change it again — there's no way to set different defaults per account.

Changing font size for replies and forwarded messages

When you reply to or forward an existing message, Outlook typically keeps the original message in its original size and puts your new text in your default font size. This means your reply might look like it has two different sizes — the quoted text above and your new text below. This is normal behavior and helps readers see what you wrote versus what was in the original message.

If you want your reply text to match the size of the original message, you can manually select your new text after typing and change its size using the formatting toolbar. In Windows Outlook, highlight your text and use the font size dropdown in the toolbar. In Outlook on the web, do the same in the compose window's formatting menu.

Troubleshooting: Font size not changing

If you've changed the default font size but new messages still appear in the old size, make sure you've saved your changes properly. In Windows, click OK on every dialog that opens — if you click Cancel or close a window without confirming, your changes won't stick. On Mac, close the Preferences window completely to may support the change takes effect.

Another common issue: you may have set the default for New Mail Messages but not for Replies and Forwards. In Windows Outlook, the Stationery and Fonts dialog has separate sections for each. Make sure you've set the size in both places if you want consistency across all outgoing messages. If you're still seeing the wrong size after checking both settings, try closing and reopening Outlook completely — sometimes the app needs to restart to explore font changes.

Frequently Asked Questions

Can I set different default font sizes for different email accounts?

No. Outlook applies the same default font size to all accounts in the same installation. If you need different sizes for different accounts, you would need to manually change the size each time you switch accounts, or use separate Outlook installations — which most people don't do.

Will changing my default font size affect emails I've already sent?

No. Changing the default only affects new messages you compose from that point forward. Sent messages keep their original formatting. The recipient sees what you sent, not what your current default is.

What's the difference between font size and zoom?

Font size is the actual size of the text in your message. Zoom is how large the message appears on your screen while you're reading or composing it. Changing the default font size changes what you send; zooming only changes what you see locally.

Why does my reply look like two different sizes?

Outlook puts your new text in your default font size and keeps the original message in its original size. This is intentional — it helps readers see what you added versus what was already there. You can manually select and resize your reply text if you want it to match.

Does Outlook on the web save my font size choice for next time?

No. Outlook on the web does not have a persistent default font size setting. You must select the size each time you compose a new message. If you use Outlook on the web regularly and want a consistent size, consider using the desktop app instead, which does remember your default.