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- Shows the digits of π to 10, 50, 100, 500, 1,000 or 5,000 decimal places.
- Calculates the digits live in your browser, accurately, using Machin’s formula.
- Multiplies or divides any number by π.
- Finds a circle’s circumference and area, and a sphere’s volume, from the radius.
How to use the pi calculator
Choose a mode
Digits of π, a number times π, or a circle from its radius.
Pick the decimal places
From 10 up to 5,000 digits.
Or enter a number or radius
For example 2 to get 2π, or a radius of 5.
Copy the result
Digits are shown in groups of 10, with the full string below.
What is pi?
Pi (π) is the ratio of a circle’s circumference to its diameter. It is the same for every circle, about 3.14159, and its decimal digits go on forever without repeating.
Circle formulas with π
Circumference = 2πr = πd
Area = πr²
Sphere volume = 4/3 πr³, Sphere surface = 4πr²
How the digits are calculated
π = 16 arctan(1/5) − 4 arctan(1/239)
This is Machin’s formula from 1706. The calculator evaluates it with exact big-number arithmetic, so every digit shown is correct.
The first 50 decimal places
Memorise as many as you like.
- π 3.14159265358979323846264338327950288419716939937510
Digits 991 to 1,000 are 2164201989.
Quick values
Using π in calculations.
- 2π 6.2831853072
- Circle with radius 5: circumference 31.415927
- Circle with radius 5: area 78.539816
Where a pi calculator helps
Pi Day and challenges
Get as many digits as you need for March 14 or a memory contest.
Geometry homework
Find circumference, area and volume quickly.
Programming
Copy a long, accurate value of π for tests.
Curiosity
See how often each digit appears in the expansion.
For full circle and shape calculations, use the area calculator or the volume calculator. Work in radians with the trig calculator.
Pi calculator FAQ
What is the value of pi?
About 3.14159265358979. It is an irrational number, so its decimal digits never end or repeat.
How many digits of pi are there?
Infinitely many. Computers have calculated trillions, but about 40 digits are enough for almost any real-world calculation.
Is 22/7 equal to pi?
No. 22/7 = 3.142857…, which is close to π but slightly too large. 355/113 is a much closer fraction.
How is pi calculated?
With formulas that converge quickly, such as Machin’s formula used here, or modern series used by supercomputers.
When is Pi Day?
March 14 (3/14), chosen because π starts 3.14.
How many digits can this calculator show?
Up to 5,000 decimal places, calculated in your browser in a fraction of a second.