How accurate is Pi in Excel and is it enough?

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Does Excel have enough significant digits for Pi in the inbuilt Pi() function?

Modern computing can calculate Pi to 3.14 trillion digits which is a good trick but even extreme situations only needs Pi to 15 significant digits.

What’s extreme?  How about interplanetary travel?  JPL/NASA calculate the paths of probes to Mercury, Mars, Jupiter and beyond.  They ‘only’ need 15 significant digits or 3.141592653589793 .

As Marc Rayman from NASA explains, working out distances on Earth using Pi to 15 places gives accuracy less than your average molecule’s width.

As part of a misspent youth, our Editor-in-Chief Peter Deegan memorized Pi to twenty decimal places – double the number someone bet he couldn’t do.  That’s nothing compared to people who can recite Pi to a hundred or more digits.

PI() accuracy in Excel

Excel’s PI() function returns 14 decimal places or 3.14159265358979

It’s the maximum precision possible in Excel (15 digits in total)

That’s the same in Excel for Windows, Mac, Apple and Android – as it should be.

14 decimal places should be enough for almost any Excel user.

Less accurate PI()

If you don’t need all 14 decimal places for PI, the Round() function will adjust to the lower accuracy you need e.g.  =ROUND(PI(),5) will return Pi rounded to 5 decimals.

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