Pi Day 2026: How the infinite number actually affects our daily lives in Leeds
We’ve just had British Pie Week - a glorious celebration of shortcrust and gravy - but today we’re swapping the pastry for the most famous constant in the universe.
It’s Pi Day, a date chosen because of the (admittedly annoying) American date format: 3.14, and while we usually roll our eyes at US standards, there is no ignoring the significance of this number in 2026.
As the UK’s inaugural City of Maths, Leeds is currently the national capital for all things numerical, proving that ‘doing the math’ is about much more than a classroom whiteboard.
For most of us, memories of Pi involve a dusty geometry textbook and a feeling of profound boredom; we sat in double-period maths thinking, "When am I ever actually going to need to know the ratio of a circle in real life?"
But as the city transforms its skyline and cements its status as a global tech hub, the application of Pi in our everyday lives might make us look back and think, “... maybe I should have paid attention in Double Math?”
From the way your smartphone finds your location on Briggate to the precision engineering that keeps our South Bank skyscrapers standing, Pi is the invisible architecture of the modern world.
It is the bridge between a straight line and a curve, the ‘hidden code’ that allows us to build, navigate, and communicate.
As we celebrate our status as the UK City of Maths, this Saturday is the perfect time to pull back the curtain on the number that quite literally makes the world go 'round.
What is Pi?
In its simplest form, Pi (π) is a mathematical constant. It represents the ratio of a circle's circumference (the distance all the way around) to its diameter (the distance straight across).
Whether you are measuring a small coin, a massive bicycle wheel, or an entire planet, the result is always the same: 3.14159…
Pi wasn't invented by a single person; it was discovered independently by ancient civilisations who noticed that the relationship between a circle's edge and its width was always constant.
Over 4,000 years ago, the ancient Egyptians and Babylonians used rough approximations like 3.125 or 3.16.
They knew the ratio existed, but they hadn't yet pinned down its true value.
The first person to calculate Pi with real mathematical rigour was the Greek mathematician Archimedes around 250 BCE. Without the help of a calculator, he ‘trapped’ a circle between two many-sided polygons to prove that the value sat somewhere between 3.1408 and 3.1429.
While the constant was known for millennia, the actual Greek letter π (derived from the Greek word for "perimeter") wasn't used to represent it until 1706 by William Jones, and it was later made famous by the mathematician Leonhard Euler.
Today, we recognise Pi as an ‘irrational’ number, meaning it never ends and never settles into a repeating pattern. For thousands of years, humans have used this infinite number to understand the fundamental geometry of our physical world.
Why is Pi so important to mathematicians?
For mathematicians, Pi is much more than just a tool for circles; it is a fundamental constant that appears in almost every branch of science.
It is "transcendental," meaning it isn’t the solution to any simple algebraic equation, making it a source of endless fascination.
Beyond basic geometry, Pi is essential in Trigonometry to describe waves and oscillations, and in Statistics to calculate the ‘Normal Distribution.’
It even appears in the natural world, describing the way rivers meander or how DNA spirals. It is the universal constant that proves nature follows a logical, mathematical script.
Is Pi somehow related to the Golden Ratio or Fibonacci Sequence?
While Pi (3.14) and the Golden Ratio (1.618) are mathematically distinct, they often show up at the same party; they are both ‘irrational’ numbers that describe the fundamental growth patterns of the universe.
Mathematically, the closest ‘direct’ link is found in the geometry of the Pyramids of Giza.
If you take the perimeter of the base of the Great Pyramid and divide it by twice its height, the result is incredibly close to Pi.
Similarly, the ratio of the slant height to half the base width is almost exactly the Golden Ratio. Whether this was intentional by ancient engineers or a natural byproduct of sophisticated geometry remains one of history’s greatest debates.
What everyday uses would I need Pi for?
You might not be performing long division on your morning commute, but you are utilising the power of Pi every single second:
GPS and Navigation
Your smartphone uses Pi-based calculations to account for the curvature of the Earth, ensuring digital maps are accurate to within a few meters.
The Internet and Radio
Wi-Fi and mobile signals travel in waves. The complex math used to process those signals and deliver data to your devices relies entirely on Pi.
Modern Medicine
Life-saving technology like MRI and CT scanners use algorithms involving Pi to translate raw data into the 3D images used by doctors.
Travel and Safety
Your car’s speedometer calculates speed based on the circumference of your tires—a calculation impossible without Pi. Even aircraft flight paths are plotted using Pi to account for the Earth's spherical shape.
Food - especially Pizza
Because the crust is the circumference and the toppings are the area, Pi helps chefs calculate the perfect ratio of dough-to-topping; if you increase the diameter of your pizza, the area increases exponentially, meaning a 20-inch pizza is actually more than twice the food of a 10-inch one.