If you need the value of π in a formula, the PI function in Google Sheets hands it to you. It takes no arguments and returns 3.14159265358979 to 15 digits of precision.
In this article, I’ll show you four practical examples that wrap PI inside circle, sphere, and radian formulas you’ll actually use.
PI Function Syntax in Google Sheets
Here is how you write the PI function.
=PI()
- The function takes no arguments. The empty parentheses are required.
PI on its own just returns the constant. You’ll usually use it inside a larger formula for geometry, trigonometry, or radian conversions.
When to Use PI Function
- Calculating the area or circumference of a circle.
- Computing the volume or surface area of a sphere or cylinder.
- Converting degrees to radians (or back) before feeding into SIN, COS, or TAN.
- Any time you need π without typing it out and risking a precision drop.
Example 1: Calculate the area of a circle
Let’s start with the most familiar use of PI, the area of a circle.
Below is the dataset, a column of radius values in A2 to A6.
The goal is to compute the area for each radius using the formula π·r².
Here is the formula:
=PI()*A2^2
PI() returns the constant, the ^2 operator squares the radius, and the multiplication gives the area. A radius of 2 produces about 12.57, a radius of 10 produces about 314.16.
Example 2: Calculate the circumference of a circle
The circumference formula is 2·π·r, another classic.
Below is the dataset, a column of radius values in A2 to A6.
The goal is to get the circumference for each circle.
Here is the formula:
=2*PI()*A2
Multiply 2 by PI() by the radius. A radius of 3 gives about 18.85, a radius of 15 gives about 94.25.
Pro Tip: Wrap the result in ROUND if you only want a few decimal places, like `=ROUND(2*PI()*A2, 2)`. Same calculation, cleaner display.
Example 3: Convert degrees to radians using PI
SIN, COS, and TAN in Google Sheets expect radians, not degrees. PI gives you a quick conversion.
Below is the dataset, angles in degrees in A2 to A6.
The goal is to convert each angle to radians.
Here is the formula:
=A2*PI()/180
Multiply the degree value by π and divide by 180. 30° becomes about 0.524 radians, 90° becomes about 1.571, and 180° becomes π itself.
Pro Tip: Google Sheets also has a built-in RADIANS function for the same job. RADIANS(A2) and A2*PI()/180 produce the same value, so use whichever you prefer.
Example 4: Calculate the volume of a sphere
For a sphere, the formula is (4/3)·π·r³.
Below is the dataset, radius values in A2 to A6.
The goal is to compute the sphere volume for each radius.
Here is the formula:
=(4/3)*PI()*A2^3
The (4/3) factor sits in its own parentheses so the division happens first. Multiply by PI(), then by r-cubed. A radius of 5 gives about 523.60, a radius of 10 gives about 4188.79.
Tips & Common Mistakes
- Don’t forget the empty parentheses – typing
=PIwithout the()returns a #NAME error. The parentheses tell Sheets you’re calling the function. - PI is fixed at 15 digits – the function returns 3.14159265358979. Don’t try to manually type more digits in your formulas. Just call PI().
- Order of operations matters – fractions like
(4/3)need their own parentheses so they evaluate before the multiplication, otherwise you’ll get the wrong result.
PI is one of those tiny functions that disappears into bigger formulas. Once you stop typing 3.14159 by hand and start calling PI(), your geometry and trig formulas get cleaner and more accurate.
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