Mu / Micro Symbol (µ μ): How to Type It Everywhere

Short answer: Tap a symbol below to copy it. To type it: on Windows, Alt + 0181 = µ (micro sign), Alt + 956 = μ (Greek mu); on Mac, Option + M = µ; in Word, type 00B5 (µ) or 03BC (μ) then Alt + X; in HTML use µ (µ) or μ (μ).

Mu is the 12th Greek letter — see the whole set in the Greek alphabet guide, or get any letter’s codes from the Alt Code Finder.

Mu (Μ uppercase, μ lowercase, pronounced “mew”) is the 12th letter of the Greek alphabet. You’ll meet it most often as the “micro” prefix — µm, µg, µF — and as the symbol for the mean in statistics and the coefficient of friction in physics. But there’s a well-known catch: two different characters look almost identical.

The micro symbol used in units like micrometre, microgram and microfarad

µ vs μ — micro sign vs Greek mu

There are two nearly identical characters:

µ — the micro sign (U+00B5), a legacy character from the old Latin-1 set. Windows types it with Alt + 0181; its HTML entity is µ.
μ — the Greek small letter mu (U+03BC), the actual Greek letter. Windows types it with Alt + 956; its HTML entity is μ.

They look the same and are used interchangeably in everyday text. The official SI symbol for the micro prefix is the Greek mu (μ), but the micro sign (µ) is extremely common for units and is the named HTML entity for “micro.” It matters mainly in strict contexts — databases, journals, search filters, scientific software — where the two are treated as different characters. Rule of thumb: for a maths variable (mean, friction) use μ; for units, either displays, but check what your system or publisher expects.

Quick reference

Symbol	Name	Windows	Mac	HTML	Unicode
µ	Micro sign	Alt + 0181	Option + M	`µ`	U+00B5
μ	Greek small mu	Alt + 956	Viewer / Greek input	`μ`	U+03BC
Μ	Greek capital mu	Alt + 924	Viewer / Greek input	`Μ`	U+039C

Type mu on Windows

Alt codes: hold Alt, type on the numeric keypad (Num Lock on): Alt + 0181 → µ (micro sign), Alt + 956 → μ (Greek mu), Alt + 924 → Μ. Micro sign also works as Alt + 230 (legacy).
Word: type 00B5 + Alt + X for µ, or 03BC + Alt + X for μ. You can also add an AutoCorrect entry so \mu expands automatically, or use an equation (Alt + =) with \mu.

Type mu on Mac

µ (micro sign): press Option + M — the quickest one.
μ (Greek mu): open the Character Viewer with Control + Command + Space, search “mu,” and double-click; or add the Greek input source.

Since Option + M gives the micro sign (U+00B5), use the Character Viewer when you specifically need the Greek mu (U+03BC).

Mu in Word & Excel

Word: the Alt + X method above, or Insert → Symbol — µ is in Latin-1 Supplement, μ is in Greek and Coptic.
Excel: use Insert → Symbol (or paste); the Alt + X trick doesn’t work in Excel. =UNICHAR(181) returns µ and =UNICHAR(956) returns μ if you’d rather generate it in a formula.

Mu in HTML & LaTeX

HTML: µ → µ (or µ), and μ → μ (or μ). Use µ when you specifically mean the micro sign.
LaTeX (math mode): \mu gives μ. For units, the siunitx package provides \micro (as in \micro\metre).

Type mu on Linux & phone

Linux: Ctrl + Shift + U, then 00b5 (µ) or 03bc (μ), then Enter.
Phone: on many keyboards, long-press the “u” key or the microphone/symbols layer offers µ; otherwise add a Greek keyboard, or copy µ/μ from the tool above.

What mu means

The micro prefix (µ / μ) = one millionth (10⁻⁶): µm (micrometre / micron), µg (microgram), µF (microfarad), µs (microsecond), µL (microlitre), µA (microamp). It’s the only SI prefix that uses a non-Latin letter.
Medical note: for micrograms, many hospitals write “mcg” instead of µg, because a handwritten or poorly rendered µ can be misread and cause dosing errors.
Mean (μ) — in statistics, the population mean.
Coefficient of friction (μ) — in physics.
Also — magnetic permeability, dynamic viscosity, the muon particle, chemical potential and reduced mass all use μ.
“u” substitute — in electronics you’ll often see uF, uH, uA, where a plain “u” stands in for µ from the days when µ wasn’t easy to type.

Troubleshooting

Problem	Fix
Alt + 0181 gives nothing	Use the numeric keypad with Num Lock on; keep the leading zero.
µ shows as a box ▯	Font lacks the glyph — switch to Segoe UI, Arial or Cambria Math. See symbol showing as a box.
My units aren’t recognised by a database	You may have used the wrong character — try the micro sign (U+00B5, `µ`) or the Greek mu (U+03BC) depending on what the system expects.
µ turned into garbled text	An encoding mismatch (mojibake) — save the file as UTF-8.
I need the Greek mu but got the micro sign	On Mac, Option + M is the micro sign; use the Character Viewer for the Greek mu.

Recap

Windows → Alt + 0181 (µ) / Alt + 956 (μ); Word: 00B5 or 03BC + Alt + X.
Mac → Option + M (µ); Character Viewer for the Greek μ.
Web → µ (µ) / μ (μ). LaTeX → \mu.
Units → either displays; for a maths variable use μ.

Frequently asked questions

What does the mu symbol mean?

Mu is the 12th letter of the Greek alphabet, written Μ (uppercase) and μ (lowercase) and pronounced “mew.” It’s most familiar as the “micro” prefix meaning one millionth (10⁻⁶), as in µm and µg, and it also stands for the population mean in statistics and the coefficient of friction in physics.

What’s the difference between µ and μ?

They look almost identical but are different Unicode characters: µ is the micro sign (U+00B5), a legacy character from the Latin-1 set, and μ is the Greek small letter mu (U+03BC). They’re used interchangeably in everyday text, but strict systems like databases and journals treat them as distinct — so for a maths variable use the Greek mu, and for units check which one your system expects.

How do I type the micro or mu symbol on Windows?

Hold Alt and type 0181 on the numeric keypad for the micro sign µ, or 956 for the Greek mu μ, in a Unicode-aware app. In Word, you can also type 00B5 (µ) or 03BC (μ) and press Alt + X, or set up an AutoCorrect entry.

How do I type mu on a Mac?

Press Option + M for the micro sign µ. For the actual Greek letter mu μ, open the Character Viewer with Control + Command + Space and search “mu,” or add the Greek input source. Option + M produces the micro sign (U+00B5), not the Greek mu.

Which symbol should I use for micrometres or micrograms?

Either the micro sign (µ) or the Greek mu (μ) will display correctly in most apps, since they look the same. The official SI symbol is the Greek mu, but the micro sign is very common for units. In medicine, “mcg” is often written instead of µg to avoid misreading — so follow your field’s convention and be consistent.

What does μ mean in statistics and physics?

In statistics, μ is the population mean — the average of an entire population. In physics, μ commonly denotes the coefficient of friction, and it’s also used for magnetic permeability, dynamic viscosity and other quantities depending on the field.

Written by Igor R.. Tested on Windows 11, macOS, Word and LaTeX. Symbol code points follow the Unicode Standard. Last updated July 2026.