Pi Day
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116 free Pi Day trivia questions with answers — science & nature quiz, new questions added Aug 2026.
50 free Pi Day trivia questions with answers. March 14 is Pi Day — the annual celebration of the mathematical constant pi (3.14159...). From ancient Babylonian clay tablets to Google Cloud supercomputers, humanity has been obsessed with this never-ending, never-repeating number for over 4,000 years. Whether you know pi to 3 digits or 300, this quiz covers everything from the basics of circles to the Chudnovsky algorithm and the Feynman point. How much do you know about the world's most famous irrational number?
30 of 116 questions with answers and explanations. Play the quiz
Q 01What date is Pi Day celebrated each year?
March 14
Pi Day is March 14, written 3/14 in month-first notation to match pi's opening digits; July 22, written 22/7, is a separate approximation date favoured in day-first countries.
Q 02What are the first three digits of pi?
3.14
The expansion continues 3.14159265... and never repeats; a room in the Palais de la Découverte in Paris has 707 of its digits on the wall.
Q 03Pi is the ratio of a circle's circumference to its what?
Diameter
Pi is a circle's circumference divided by its diameter, the same ratio for every circle; since the diameter is twice the radius, it also equals circumference over 2r.
Q 04What type of number is pi?
Irrational
Pi is irrational: it cannot be written as a fraction of two integers, a fact first proved in the 1760s, so its decimal expansion never ends or repeats.
Q 05What is the formula for the circumference of a circle?
2πr
The circumference is 2πr: the diameter is twice the radius, and the distance around any circle is pi times its diameter.
Q 06What is the formula for the area of a circle?
πr²
The area of a circle is πr², where r is the radius. This fundamental formula connects pi to every circle's area.
Q 07Which famous physicist's birthday falls on Pi Day?
Albert Einstein
Albert Einstein was born in Ulm, Germany, on March 14, 1879, and Pi Day events in his adopted American home town double as his birthday party.
Q 08What food is traditionally eaten on Pi Day?
Pie
Pie is a homophone of pi and is itself a circle, so pies have headlined the menu since the first celebration in 1988; schools and museums often add pie-eating contests.
Q 09Which state legislature nearly passed an 1897 bill implying pi equals 3.2?
Indiana
Indiana's House of Representatives passed the bill before the state Senate rejected it, so it never became law.
Q 10In what year was Pi Day first officially recognized by the U.S. House of Representatives?
2009
On March 12, 2009 the U.S. House passed a non-binding resolution designating March 14 as National Pi Day; the first large-scale celebration had come in 1988, two decades earlier.
Q 11Who organized the first large-scale Pi Day celebration in 1988?
Larry Shaw
Larry Shaw, a physicist on the staff of the science museum where he worked, organised the first celebration on March 14, 1988 and was later nicknamed the 'Prince of Pi'.
Q 12At which museum was the first Pi Day celebration held?
San Francisco Exploratorium
The Exploratorium in San Francisco, where physicist Larry Shaw worked, held the first celebration on March 14, 1988, and later made Pi Day an annual event.
Q 13Which ancient Greek mathematician is famous for his method of approximating pi using polygons?
Archimedes
Q 21Which Indian mathematician's c.1400 infinite series for pi predated Europe's by over two centuries?
Madhava
Madhava of Sangamagrama, founder of the Kerala school, found the arctangent series for pi around 1400; Europe rediscovered it through James Gregory and Leibniz in the 1670s.
Q 22Which Swiss mathematician popularized π for the circle constant from 1736 onward?
Leonhard Euler
Leonhard Euler adopted π in his 1736 Mechanica and, through his vast correspondence and his 1748 Introductio, spread the symbol across Europe until it was universal.
Q 23The ancient Greek who first trapped pi between polygons stopped at how many sides?
96
He started from hexagons and doubled four times (6, 12, 24, 48, 96) to bound pi between 223/71 and 22/7.
Archimedes inscribed and circumscribed regular polygons around a circle, doubling their sides step by step, and squeezed pi between the bounds 223/71 and 3 1/7.
Q 14What is the fourth digit after the decimal point in pi?
5
Pi runs 3.14159265..., so the digits after the point go 1-4-1-5-9-2-6-5.
Q 15How many degrees are there in π radians?
180
π radians equals 180 degrees: a full circle of 360° measures 2π radians, and one radian is the angle whose arc length equals the radius.
Q 16Which country writes dates month-first, the format that makes 3/14 Pi Day?
United States
The United States writes dates month-first, so March 14 becomes 3/14; day-first countries such as the United Kingdom would write 14/3, which is why some mark July 22 (22/7) instead.
Q 17What does it mean that pi is a transcendental number?
Not the root of any rational polynomial
A transcendental number is not the root of any polynomial with rational coefficients; e was shown to be transcendental in 1873 and pi followed in 1882, nine years later.
Q 18What ancient civilization used the approximation 3.125 for pi around 1900 BC?
Babylonians
The value 25/8 is implied on a clay tablet; the Egyptian Rhind Papyrus from about the same era treats pi as (16/9)², roughly 3.16.
Q 19On Pi Day 2015 at 9:26:53 AM, what did the date and time together spell out?
Pi matched to 10 digits: 3.141592653
This 'Pi Instant' comes around once a century, and 2015 was billed as Super Pi Day because that year's date supplied five digits.
Q 20What is the practice of memorizing digits of pi called?
Piphilology
Piphilology, a play on 'pi' and 'philology', is the practice of memorising pi's digits; poems whose word lengths encode the digits are called piems.
Q 24What famous unsolved problem was proven impossible by the transcendence of pi?
Squaring the circle
A compass-and-straightedge construction can only produce algebraic lengths, so a square matching a circle's area is out of reach.
Q 25The "tau movement" argues that which number should replace pi as the fundamental circle constant?
2π (approximately 6.283)
Michael Hartl's 2010 Tau Manifesto argues that the ratio of circumference to radius, one full turn, is the more natural constant.
Q 26What is Euler's identity, often called the most beautiful equation in mathematics?
e^(iπ) + 1 = 0
e^(iπ) + 1 = 0 links e, i, π, 1 and 0 in one line and is a special case of Euler's formula; a 1990 poll of Mathematical Intelligencer readers named it the most beautiful theorem in mathematics.
Q 27In 1949 John von Neumann's team spent 70 hours computing 2,037 digits of pi on which computer?
ENIAC
ENIAC, the Army's electronic computer at Aberdeen Proving Ground, produced 2,037 digits in about 70 hours in 1949; that same year Wrench and Smith reached 1,120 digits with a desk calculator.
Q 28Which Indian mathematician produced pi formulas that converge extremely rapidly?
Srinivasa Ramanujan
Srinivasa Ramanujan's 1914 paper gave series for 1/π that add roughly eight correct digits per term, anticipating the fast algorithms used for record computations decades later.
Q 29Which university has often timed its admissions decision letters to arrive on Pi Day?
MIT
MIT has released its undergraduate admissions decisions on March 14 for years; in 2015 they went online at 9:26 am, that year's 'pi minute'.
Q 30Which mathematician brothers' 1988 formula, adding about 14 digits per term, pushed pi past a billion digits?
Chudnovsky
David and Gregory Chudnovsky built their 1988 algorithm on Ramanujan's series; it carried them past one billion digits in 1989 and drove the 100-trillion-digit computation of 2022.