Phi — φ Greek Letter Symbol
φ
Phi — φ / Φ
21st letter of the Greek alphabet · pronounced /faɪ/
MathematicsPhysicsEngineeringGeometry
Copy symbol
φ
Lowercase phi
Φ
Uppercase Phi
Technical reference
| Unicode (lowercase) | U+03C6 |
| Unicode (uppercase) | U+03A6 |
| HTML entity | φ |
| HTML decimal | φ |
| LaTeX | \phi |
| Python / Unicode escape | \u03c6 |
| Alt code (Windows) | Alt + 966 |
Uses in science & engineering
Golden ratio
φ = (1 + √5)/2 ≈ 1.618. Appears in geometry, art, architecture, and nature.
\(\varphi = \frac{1+\sqrt{5}}{2} \approx 1.618\)
Electric potential
Scalar potential of an electric field at a given point in space.
\(\mathbf{E} = -\nabla \phi\)
Angle of internal friction (geotechnical)
Key parameter in soil mechanics describing shear strength of soils.
\(\tau_f = c + \sigma \tan\phi\)
Magnetic flux (Φ)
Uppercase Phi denotes total magnetic flux through a surface.
\(\Phi = \int \mathbf{B} \cdot d\mathbf{A}\)
Spherical coordinate angle
Polar angle (colatitude) in spherical coordinate systems.
\((r, \theta, \phi)\)
Related symbols
How to insert in applications
Windows
Best option: copy from this page.
Or press Win + . to open emoji & symbols panel.
Alt codes work only in Word/Notepad with NumLock on and English layout — not in browsers.
Or press Win + . to open emoji & symbols panel.
Alt codes work only in Word/Notepad with NumLock on and English layout — not in browsers.
macOS
Press ⌃⌘Space → Character Viewer → search “phi”
Microsoft Word
Type 03c6 then press Alt+X
Google Docs
Insert → Special characters → search by name
Excel
Insert → Symbol → Subset: Greek → select symbol
LaTeX
Use in math mode: $ … $
Python
Use Unicode escape or chr()
HTML / CSS
Use HTML entity or decimal code