The micro sign µ is Alt+0181 on Windows and Option+M on a Mac. It is the SI prefix for one millionth, as in µm and µF. Unicode also has a Greek mu at U+03BC that looks the same, and the two are separate characters that sort differently.
01 All shortcuts at a glance
| Platform | Shortcut | |
|---|---|---|
| Windows (Alt code) | Hold Alt, type 0181 on the numpad |
|
| Windows (any app) | Win+. or Win+; emoji/symbol picker, or Character Map (Win+R → charmap) |
|
| Mac | Control+Command+Space to open Character Viewer, search "Micro Sign" |
|
| Word / Outlook | Type 00B5, then press Alt+X |
|
| Linux (IBus) | Ctrl+Shift+U, then 00b5, then Enter |
|
| HTML / CSS | µ · \00b5 (CSS) |
02 Step by step, per platform
A real, followable procedure for every platform, not a thin restatement of the shortcut.
Windows
- Make sure Num Lock is on.
- Hold Alt and type 0181 on the numeric keypad.
- Release Alt, µ appears.
Mac
- Press Control+Command+Space to open the Character Viewer.
- Type "Micro Sign" in the search field.
- Double-click the result to insert it.
Microsoft Word
- Type 00B5.
- Press Alt+X immediately after, it converts the hex code to µ.
03 Characters in this set
04 Troubleshooting & confusables
| Looks like it | But it's actually | When to use |
|---|---|---|
| μ (U+03BC) | Greek small letter mu | For Greek text and mathematical variables. The micro sign is the legacy compatibility character. |
| u as a substitute | The letter u | A long-standing ASCII workaround, as in um for micrometre. Acceptable in code comments only. |
| mc as a prefix | A written abbreviation | Required on medical prescriptions, where µg is banned as a misreading hazard. |
05 FAQ
What is the Unicode code point for the micro sign?
It is U+00B5, decimal 181. Alt+0181 types it on Windows. The visually identical Greek mu is a different character at U+03BC.
Which one should I use for units?
Either renders correctly, but Unicode normalisation folds the micro sign to the Greek mu, so text search may treat them as one or as two depending on the system. For SI units, the micro sign at U+00B5 is what Alt+0181 gives you and is widely accepted.
What does the prefix mean?
One millionth, or 10 to the power of minus six. So a micrometre is a millionth of a metre, and a microsecond is a millionth of a second.
Why do prescriptions write mcg instead of µg?
Handwritten µ is easily misread as m, which would be a thousandfold dosing error. Safety guidance in several countries therefore requires the spelled-out mcg.
How do I type it on a phone?
Press and hold the m key on some layouts, or switch to a Greek keyboard for the mu. Copying it is usually quicker.