Phi Symbol Copy and Paste (φ Φ ϕ)
Small phi
Unicode U+03C6 · HTML φ · Alt code Alt+237
Tap any symbol to copy it. Each tap also adds it to the box above, so you can copy several together.
Codes for every symbol on this page (Unicode, HTML, Alt, Mac, Word)
| Symbol | Name | Unicode | HTML | Windows Alt code | Mac | MS Word |
|---|---|---|---|---|---|---|
| φ | Small phi | U+03C6 | φ | Alt+237 | - | 03C6 then Alt+X |
| Φ | Capital phi | U+03A6 | Φ | Alt+232 | - | 03A6 then Alt+X |
| ϕ | Phi variant (straight) | U+03D5 | ϕ | - | - | 03D5 then Alt+X |
| ɸ | Phonetic phi | U+0278 | ɸ | - | - | 0278 then Alt+X |
| ⌀ | Diameter sign | U+2300 | ⌀ | - | - | 2300 then Alt+X |
The phi symbol φ is the 21st letter of the Greek alphabet, and its capital form is Φ. A circle with a line through it, phi is famous in maths as the golden ratio and in physics as the symbol of magnetic flux.
The grid holds five characters: small φ, capital Φ, the alternative ϕ, the phonetic letter ɸ and the diameter sign ⌀. They look alike but are not interchangeable, and this page shows which one to pick.
Phi Symbol in Maths: The Golden Ratio
The best-known phi symbol in maths is the golden ratio:
φ = (1 + √5) ÷ 2 ≈ 1.618
Divide a line into two parts so that the whole line ÷ longer part = longer part ÷ shorter part. That ratio is φ. It has some neat properties:
- φ² = φ + 1 (so φ² ≈ 2.618)
- 1 ÷ φ = φ − 1 ≈ 0.618
- Divide one Fibonacci number by the one before it (89 ÷ 55, 144 ÷ 89) and the answer gets closer and closer to φ.
Other maths uses of φ: an angle in polar and spherical coordinates, and Euler's phi function φ(n) in number theory, which counts the numbers up to n that share no factor with n. For example, φ(10) = 4 (1, 3, 7 and 9).
Magnetic Flux Symbol Φ in Physics
Capital Φ is the symbol of magnetic flux. Magnetic flux is the amount of magnetic field passing through an area:
Φ = B A cos θ
Its SI unit is the weber (Wb). Faraday's law says an EMF is produced when Φ changes: e = −dΦ/dt. This idea powers generators and transformers, and it is a big part of the Class 12 chapter on electromagnetic induction.
Other places you meet the phi symbol in physics:
| Symbol | Meaning | Chapter |
|---|---|---|
| Φ or Φ_B | Magnetic flux | Electromagnetic induction |
| Φ_E | Electric flux (Gauss's law) | Electrostatics |
| φ | Phase angle, as in y = A sin(ωt + φ) | Waves, AC circuits |
| φ₀ or φ | Work function | Photoelectric effect |
| φ (or V) | Electric potential | Electrostatics |
The ω in the phase formula is covered on the omega symbol page.
φ, ϕ, ɸ and ⌀: Spot the Difference
- φ (U+03C6): the normal small phi. In many fonts it is drawn with a loop.
- ϕ (U+03D5): the same letter drawn with a straight line through a circle. Maths papers sometimes use both styles for two different quantities.
- ɸ (U+0278): a phonetic letter used in the International Phonetic Alphabet for a sound made with both lips, a bit like blowing out a candle.
- ⌀ (U+2300): the diameter sign used on engineering drawings, as in ⌀20 mm. It is not a Greek letter. See the diameter symbol page.
Also do not confuse phi with the empty set sign ∅ in set theory, which is a separate maths character.
How to Type the Phi Symbol in Word and on Your Keyboard
Phi is lucky: both small and capital have old DOS Alt codes.
| Method | φ | Φ |
|---|---|---|
| Windows Alt code (number pad) | Alt+237 | Alt+232 |
| Phi symbol in Word | 03C6 then Alt+X | 03A6 then Alt+X |
| HTML | φ | Φ |
For ϕ use 03D5 then Alt+X. Inside a Word equation, \phi and \varphi give the two styles, though which one looks loopy depends on the font. On a Mac there is no Option key for phi, so open Character Viewer with Control+Command+Space. In Google Docs, use Insert > Special characters.
Phi often appears next to other circle-based constants, so you may also want the pi symbol. The full set of 24 letters is on our Greek letters page.
Frequently asked questions
What is the symbol of phi?
The symbol of phi is φ in small letters and Φ in capital letters. Small φ is common for angles and the golden ratio; capital Φ is used for flux.
How do you pronounce phi?
In English it is said "fy" (rhymes with "pie") or "fee". Both are common in India. In modern Greek it is "fee".
What is the value of phi?
As the golden ratio, φ is about 1.618034. It is an irrational number, so its decimal never ends or repeats.
Is the phi symbol the same as the diameter symbol?
No. Phi is a Greek letter, while ⌀ is a technical drawing sign for diameter. They look similar, but use ⌀ on drawings and φ or Φ in equations.
What is the symbol of magnetic flux and its unit?
Magnetic flux is written Φ (or Φ_B) and measured in webers (Wb). One weber equals one tesla multiplied by one square metre.