Theta Symbol (θ Θ): How to Type It Everywhere

Short answer: Tap a theta below to copy it. To type it: on Windows, Alt + 952 = θ, Alt + 920 = Θ (numeric keypad); on Mac, open the Character Viewer (Control + Command + Space) and search “theta,” or add the Greek input source; in Word, type 03B8 then Alt + X; in HTML use θ / Θ; in LaTeX use \theta / \Theta.

Theta is the 8th Greek letter — see the whole set in the Greek alphabet guide, or get any letter’s codes from the Alt Code Finder.

Theta (Θ uppercase, θ lowercase) is the 8th letter of the Greek alphabet, and if you’ve ever done trigonometry you already know it: θ is the go-to symbol for an angle — sin θ, cos θ, tan θ. There’s also a second lowercase shape you’ll meet in maths.

θ vs ϑ — the two theta shapes

Lowercase theta has two forms:

θ — the standard lowercase (U+03B8). This is the one you want almost always.
ϑ — the “script” or variant theta (U+03D1), an alternative shape some maths texts use for the same letter. In LaTeX it’s \vartheta.

They’re the same letter; if you’re unsure, use θ.

Theta used to label an angle in a right triangle

Quick reference

Symbol	Name	Windows	Mac	HTML	LaTeX	Unicode
θ	Greek small theta	Alt + 952	Viewer / Greek input	`θ`	`\theta`	U+03B8
Θ	Greek capital theta	Alt + 920	Viewer / Greek input	`Θ`	`\Theta`	U+0398
ϑ	Theta variant	Alt + 977	Viewer	`&thetasym;`	`\vartheta`	U+03D1

Type theta on Windows

Alt codes: hold Alt, type on the numeric keypad (Num Lock on): Alt + 952 → θ, Alt + 920 → Θ, Alt + 977 → ϑ. Use a Unicode-aware app (Word, browsers, email).
Word: type 03B8 and press Alt + X for θ, or 0398 + Alt + X for Θ. In an equation (Alt + =), type \theta or \Theta then Space.
Picker: Win + . opens the emoji/symbol panel; or use Character Map.
Lots of Greek: add the Greek keyboard and switch with Windows + Space.

Type theta on Mac

Macs have no direct Option shortcut for theta — so:

Character Viewer: press Control + Command + Space, search “theta,” and double-click θ or Θ.
Greek input source: add it under System Settings → Keyboard → Input Sources for regular Greek typing.

Note: you may see it claimed that Option + J types theta on a Mac — it doesn’t. Option + J produces the increment sign ∆ (see delta symbol). Use the Character Viewer instead.

Theta in Word

The 03B8 + Alt + X method above is quickest; otherwise Insert → Symbol → (Greek and Coptic), or use an equation (Alt + =) with \theta / \Theta for properly formatted maths.

Theta in HTML & LaTeX

HTML: θ → θ, Θ → Θ, &thetasym; → ϑ; numeric fallbacks θ / Θ (or hex θ / Θ) render the same.
LaTeX (math mode): \theta for θ, \Theta for Θ, \vartheta for the variant ϑ.

Type theta on Linux & phone

Linux: Ctrl + Shift + U, then 03b8 (θ) or 0398 (Θ), then Enter.
Phone: add a Greek keyboard (iPhone: Settings → General → Keyboard; Android: Gboard languages) and switch with the globe key, or copy θ/Θ from the tool above.

What theta means

Angles (θ) — the classic use, in geometry and trigonometry: the angle between two rays, lines or vectors, and the variable inside sin θ, cos θ and tan θ. It’s the default name for an unknown angle.
Polar & spherical coordinates — θ is the angular coordinate.
Physics — phase angle, angular displacement and angular position.
Computer science (Θ) — capital theta is Big-Theta notation, a tight bound on an algorithm’s running time, Θ(n).
Finance — “theta” is an options Greek measuring time decay (how much an option loses per day) in the Black–Scholes model.
Statistics — θ often denotes an unknown parameter to be estimated.
Temperature — θ is sometimes used for temperature (for example potential temperature, or the Debye temperature Θ).

Troubleshooting

Problem	Fix
Alt + 952 gives the wrong character	Use the numeric keypad with Num Lock on, in a Unicode-aware app.
θ shows as a box ▯	Font lacks the glyph — switch to Segoe UI, Arial or Cambria Math. See symbol showing as a box.
Option + J gave me ∆, not θ	Option + J is the increment sign, not theta. Use the Character Viewer (Control + Command + Space) on Mac.
θ vs ϑ look different	They’re the same letter in two shapes (U+03B8 vs U+03D1). Use θ unless a formula specifically calls for ϑ.
θ looks like a “0” with a line	That’s correct — keep it distinct from a zero or the Danish/Norwegian ø.

Recap

Windows → Alt + 952 (θ) / Alt + 920 (Θ); Word: 03B8 + Alt + X.
Mac → Character Viewer (Control + Command + Space) — no Option shortcut.
Web → θ / Θ. LaTeX → \theta / \Theta, \vartheta for ϑ.

Frequently asked questions

What does the theta symbol mean?

Theta is the 8th letter of the Greek alphabet, written Θ (uppercase) and θ (lowercase). It’s best known as the symbol for an angle in geometry and trigonometry — the θ in sin θ, cos θ and tan θ — and it also appears for phase angles, statistical parameters and, as capital Θ, Big-Theta notation in computer science.

What’s the difference between θ and ϑ?

They’re two shapes of the same letter. θ (U+03B8) is the standard lowercase theta, and ϑ (U+03D1) is a “script” or variant theta used in some mathematical texts. They mean the same thing; unless a formula specifically calls for the variant (LaTeX \vartheta), use θ.

How do I type theta on Windows?

Hold Alt and type 952 on the numeric keypad for θ, or 920 for Θ, in a Unicode-aware app. In Word, you can also type 03B8 (or 0398) and press Alt + X, or use the Win + . picker. For lots of Greek, add the Greek keyboard layout.

How do I type theta on a Mac?

Macs have no direct Option shortcut for theta. Open the Character Viewer with Control + Command + Space, search “theta,” and insert θ or Θ, or add the Greek input source for regular Greek typing. (Option + J does not type theta — it produces the increment sign ∆.)

What does θ mean in trigonometry?

In trigonometry, θ represents an angle — typically the unknown or variable angle in a triangle or on the unit circle. You’ll see it inside the trigonometric functions sin θ, cos θ and tan θ, where the value depends on the size of that angle.

What is Θ (capital theta) used for?

Capital Θ is most famous in computer science as Big-Theta notation, which describes a tight bound on an algorithm’s running time, written Θ(n). It’s also used as a variable and, in some fields, for temperature.

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