Pi Symbol (Π π): Meaning, Uses and Copy Paste
| Uppercase / lowercase | Π / π |
| Variant form | ϖ (U+03D6) |
| Position in alphabet | 16 of 24 |
| Unicode | U+03A0 / U+03C0 |
| HTML entity | Π / π |
| HTML decimal | Π / π |
| LaTeX | \Pi / \pi |
| Word (type code, then Alt+X) | 03A0 / 03C0 |
| Windows Alt code | Alt + 227 (π) |
| Greek numeral value | 80 |
The pi symbol (Π π) is the sixteenth letter of the Greek alphabet, and lowercase π is the most famous constant in mathematics. It equals the ratio of a circle’s circumference to its diameter, about 3.14159.
Capital Π has its own job, too, as the product sign. This guide explains both, along with their history and the fastest ways to type them.
What the Pi Symbol Means
As a letter, pi makes the “p” sound. It sits sixteenth in the alphabet, after omicron and before rho. In the Greek numeral system, pi stood for 80.
The letter came from the Phoenician letter pe. From Greek, it passed into Latin as P and into Cyrillic as П. Americans say PIE, while Greeks say PEE.
Pi as a Number
In math, π means the circumference of any circle divided by its diameter. The ratio is the same for every circle, about 3.14159.
Moreover, π is irrational, so its decimals never end or repeat. Britannica’s entry on pi covers its long history of approximations.
Everyday work rarely needs many digits. For example, 3.14 or 22/7 is close enough for most school problems. Engineers and scientists, however, use more digits when precision matters.
Where the Symbol Came From
Ancient mathematicians studied the ratio long before it had a symbol. Archimedes, for instance, showed that it lies between 3 10/71 and 3 1/7. Yet nobody used a Greek letter for it until the 1700s.
The Welsh mathematician William Jones first used π for the ratio in 1706. As History Today explains, he printed it in his book Synopsis Palmariorum Matheseos. Later, Leonhard Euler used the symbol in his widely read works, and it soon became standard.
Quick fact: Jones probably chose π because it is the first letter of the Greek words for “periphery” and “perimeter.” Sources describe this as the likely reason rather than a stated one.
Uppercase vs Lowercase Pi
Capital pi (Π) looks like a doorway with two legs and a flat top. Lowercase pi (π) is smaller, and its top bar often extends past the legs. Neither form looks like a Latin letter, so pi is easy to recognize.
The Variant ϖ
There is also a rare variant, ϖ, sometimes called pomega because it looks like omega with a bar. It is a historical handwriting form of lowercase pi. Today it appears mainly in astronomy and physics, for example as the longitude of pericenter in orbital mechanics.
Lookalikes to Avoid
| Character | Name | Code point |
|---|---|---|
| Π | Greek capital pi | U+03A0 |
| π | Greek small pi | U+03C0 |
| ϖ | Greek pi symbol | U+03D6 |
| ∏ | N-ary product | U+220F |
| П | Cyrillic capital Pe | U+041F |
The n-ary product sign ∏ is the large operator used in formulas. It looks like Π but is a separate math symbol, just as ∑ is separate from Greek Sigma.
Pi in Math and Science
Beyond the circle constant, both forms of pi have standard meanings. The table below lists the most common ones. For more letters used in equations, see our guide to Greek letters in math.
| Symbol | Field | Meaning |
|---|---|---|
| π | Geometry | Circle constant, about 3.14159 |
| Π | Algebra | Product of a sequence |
| π(x) | Number theory | Number of primes up to x |
| Π | Chemistry | Osmotic pressure |
| π | Particle physics | Pion, a type of meson |
| π | Economics | Profit or inflation rate |
| π | Machine learning | Policy in reinforcement learning |
Circle Formulas
Pi appears in every circle formula. The circumference is C = 2πr, and the area is A = πr². Similarly, a sphere has volume V = (4/3)πr³.
Some mathematicians argue that 2π deserves its own symbol, because full turns use it so often. They propose tau (τ) for that value, although π remains the standard.
Pi vs Phi
Students sometimes mix up pi with phi (φ), because the names sound alike. However, they are different constants. Pi is about 3.14159 and comes from circles, while phi usually means the golden ratio, about 1.618.
Both numbers are irrational, and both show up in geometry. Still, π governs circles and waves, whereas φ appears in proportions such as the regular pentagon.
Why Pi Shows Up Everywhere
Pi appears far beyond circles. For example, it shows up in the normal distribution in statistics, in wave equations and in electrical formulas for alternating current. The reason is that circles and rotation hide inside many processes that repeat.
Product Notation
Capital Π multiplies a list of terms, just as Σ adds them. For example, the product of k from 1 to 5 equals 120. Our page on sigma notation explains the matching summation rules.
How to Type the Pi Symbol
Pi is one of the easiest Greek letters to type, because both Windows and Mac have built-in shortcuts. Still, the capital form needs a different method.
- Windows alt code: Hold Alt and type 227 on the numeric keypad for π. Capital Π has no alt code. See our Greek alt codes chart.
- Microsoft Word: Type
03C0and press Alt+X for π, or03A0then Alt+X for Π. - Mac: Option+P gives the real Greek π (U+03C0). However, Option+Shift+P gives ∏, the product sign, not Greek Π. Our Mac typing guide has more detail.
- LaTeX: Type
\pifor π,\Pifor Π and\varpifor ϖ. For a product operator, use\prod. Our LaTeX command list covers every letter. - HTML: Use
πorπfor π,ΠorΠfor Π andϖorϖfor ϖ.
Tip: On a phone, the quickest route is often to add a Greek keyboard and tap P. Otherwise, copy π from the symbol card at the top of this page.
Pi in Culture
Few numbers have a fan base like this one. Every year, Pi Day falls on March 14, written 3/14 in the US. Physicist Larry Shaw held the first celebration at San Francisco’s Exploratorium in 1988.
In 2009, the US House of Representatives passed a resolution recognizing National Pi Day. The date is also Albert Einstein’s birthday, so Princeton, New Jersey, celebrates both together. Fans mark the day with pie, digit-reciting contests and math games.
Pi also shows up in film and books. For instance, Darren Aronofsky’s 1998 film Pi follows a mathematician obsessed with patterns. Yann Martel’s novel Life of Pi, meanwhile, uses the letter as its hero’s nickname.
Pi Symbol Quick Reference
Use this table to copy the right pi symbol code. All values match the Unicode Greek and Coptic chart.
| Item | Uppercase Π | Lowercase π | Variant ϖ |
|---|---|---|---|
| Unicode | U+03A0 | U+03C0 | U+03D6 |
| HTML entity | Π | π | ϖ |
| HTML decimal | Π | π | ϖ |
| LaTeX | \Pi | \pi | \varpi |
| Windows alt code | None | Alt+227 | None |
| Word Alt+X | 03A0 | 03C0 | 03D6 |
| Mac shortcut | None | Option+P | None |
| Numeral value | 80 | 80 | — |
Frequently Asked Questions
What does the pi symbol mean?
Lowercase π is the ratio of a circle’s circumference to its diameter, about 3.14159. As a letter, Pi (Π π) is the sixteenth letter of the Greek alphabet and makes a “p” sound.
What is the alt code for pi?
Hold Alt and type 227 on the numeric keypad to get π. Capital Π has no alt code, so type 03A0 in Word and press Alt+X instead.
How do you type π on a Mac?
Press Option+P on a US keyboard. Unlike most Mac Option shortcuts for Greek-looking symbols, this one gives the real Greek letter π (U+03C0).
Who first used π for the circle constant?
The Welsh mathematician William Jones used π for the ratio in 1706. Leonhard Euler later used it widely, which helped make it standard.
What does capital Π mean in math?
Capital Π marks a product, the result of multiplying a list of terms together. It works like Σ, which marks a sum.