# pi

Learn how to use the mathematical constant pi in Notion formulas.
The mathematical constant pi (
$π$
) equals (roughly) 3.1415926559.
1
pi
$π$
is the ratio between the circumference and diameter of a circle. This ratio is shared by all circles, no matter the size.
$π$
can be used to calculate the circumference and area of a circle, volume and surface area of a sphere, and more.
$π$
here:

## Example Formula

1
pi * 10
The above formula will calculate the circumference of a circle with a diameter of 10cm. It uses the simple equation
$πd$
, where
$d$
is the diameter of the circle.
In this case, the circumference would be approximately
$31.4159265cm$
.

## Example Database

In this example database, the Formula (num) property calculates the area of a circle with a given radius, set in the Circle Radius (cm) property.

### "Formula (Num)" Property Formula

1
pi * prop("Circle Radius (cm)") ^ 2
The formula to calculate the area inside a circle is
$πr^2$
. We can create this equation in a Notion formula using the code above:
• pi is the Notion constant for
$π$
• prop("Circle Radius (cm)") uses the prop() function to pull in the value of the Circle Radius (cm) Number property
• ^ 2 squares the radius of the circle
Other formula components used in this example:

### "Pretty Formula" Property Formula

1
format(round(prop("Formula (num)") * 100) / 100) + "cm²"
This formula:
1. 1.
Intakes the output of the previous formula
2. 2.
Rounds it to the nearest hundredth (i.e. two decimal places)
3. 3.
Converts the resulting number to a String
4. 4.
Appends “cm²”
Note that Notion formulas do not support text formatting, so I’m using the actual ² symbol. You can find this symbol here:
To round the decimal to two decimal places, I use the following trick:
1
round(prop("Formula (num)")*100)/100
Notion’s built-in round() function only rounds numbers to the nearest whole integer. But this trick will output a rounded number to two decimals places instead. Learn more about this trick in the round function reference.
Other formula components used in this example: