How do I calculate the area of a circle in Excel?

Use =PI()*POWER(radius, 2) or =PI()*radius^2. For a circle with radius 5: =PI()*5^2 = 78.54. For diameter, use =PI()*POWER(diameter/2, 2) or =PI()/4*diameter^2.

How do I calculate circumference using PI?

Circumference = 2πr or πd. In Excel: =2*PI()*radius or =PI()*diameter. For radius 10: =2*PI()*10 = 62.83. This is the distance around the circle.

Why doesn't PI() take any arguments?

PI() is a constant function that always returns the same value (3.14159265358979...). It doesn't need arguments because π is a fixed mathematical constant. Just use =PI() and multiply/divide as needed in your formulas.

Math & Trig

PI Function in Excel

Returns the value of pi (π) accurate to 15 digits.

Syntax

=PI()

Examples

=PI() - Value of pi - Result: 3.14159265358979
=PI()*2 - Circumference of unit circle - Result: 6.283...

PI in reporting workflows

Use absolute references when copying formulas across rows.
For conditional totals see [SUMIF](/functions/sumif/) and [SUMIFS](/functions/sumifs/).
Filtered lists may need [SUBTOTAL](/functions/subtotal/) instead of SUM on visible cells only.

Common errors

No arguments needed

Use cases

Circle calculations
Trigonometry
Geometry formulas

Frequently asked questions

How do I calculate the area of a circle in Excel? Use =PI()*POWER(radius, 2) or =PI()*radius^2. For a circle with radius 5: =PI()*5^2 = 78.54. For diameter, use =PI()*POWER(diameter/2, 2) or =PI()/4*diameter^2.
How do I calculate circumference using PI? Circumference = 2πr or πd. In Excel: =2*PI()*radius or =PI()*diameter. For radius 10: =2*PI()*10 = 62.83. This is the distance around the circle.
Why doesn't PI() take any arguments? PI() is a constant function that always returns the same value (3.14159265358979...). It doesn't need arguments because π is a fixed mathematical constant. Just use =PI() and multiply/divide as needed in your formulas.

Editorial review

Reviewed by Excel.Directory Editorial Team. Updated May 2026.