Here’s some common circle and sphere calculations that you might remember from school (or long forgotten) but now as Excel formula using Pi 𝜋 or as Excel calls it, Pi().
Many formulas rely on Pi 𝜋 so Excel has a function Pi() which inserts it to 14 decimal places. That’s accurate enough for almost any purpose including calculating planetary motions and saves everyone typing 3.14159265358979 over and over again.
Circle formulas in Excel
Formulas to work out the Circumference, Area, Arc Length and Arc Area of a circle.
Copy any of these formulas into Excel, replace the names with cell references/names and you’re good to go!
| Circle | Excel Formula |
|---|---|
| CIRCUMFERENCE from radius | =PI()*Radius*2 |
| CIRCUMFERENCE from diameter | =PI()*Diameter |
| DIAMETER from circumference | =Circumference/PI() |
| RADIUS from circumference | =Radius/PI()*2 |
| AREA from radius | =PI()*Radius^2 |
| AREA from diameter | =PI()*(Diameter/2)^2 |
| AREA from circumference | =(Circumference/PI()/2)^2*PI() |
| ARC LENGTH from radius and angle in degrees | =2*PI()*Radius*(AngleDegrees/360) |
| ARC AREA from radius and angle in degrees | =(PI()*Radius^2)*(AngleDegrees/360) |
Sphere formulas in Excel
For a sphere or ball, here’s the Excel formulas for Surface Area and Volume.
| Sphere | Excel Formula |
|---|---|
| SURFACE AREA from diameter | =PI()*(Diameter^2) |
| SURFACE AREA from radius | =PI()*(Radius*2)^2 |
| VOLUME from diameter | =PI()*Diameter^3/6 |
| VOLUME from radius | =PI()*(Radius*2)^3/6 |
Earth, Moon and Sun calcs in Excel
Here’s the sphere formulas in practice for the surface area and volume of our planet and some near neighbors.
Pedantic Note: all the above assumes the Earth, Moon and Sun are completely spherical. The Earth and its moon are both oblate spheroids (they bulge at the equator due to axis spin). The Sun also has a slight bulge but it’s unexpectedly small.
Pi 𝜋 Day
Pi 𝜋 choices in Word, Excel, PowerPoint and Outlook
