MISTAKE in calculations

[SavaS]

At first sorry for my bad English. I'm not English speaker.
I do not understand why Excel show small amount in calculations instead zero.
For example:
Open new workbook, cells format as General, enter digits by keyboard (i mean formula use just in answer cell G1)

Cell A1 - enter 26.58
Cell B1 - enter 2.18
Cell C1 - empty cell
Cell D1 - enter 22.87
Cell E1 - enter 0.2
Cell F1 - enter 1.33
Cell G1 - formula =A1-B1-C1-D1-E1-F1
get an answer -2.44249E-15 WHY???? Why not zero?

I tried with another digits
Cell A1 - enter 30.61
Cell B1 - enter 2.44
Cell C1 - empty cell
Cell D1 - enter 24.64
Cell E1 - enter 0.1
Cell F1 - enter 3.43
Answer is correct. Get zero.

Could anyone explain this. THANK YOU!!!!

 

[Eric W]

Welcome to the MrExcel forum!

The issue is how Excel stores floating point numbers. In short, Excel stores numbers in binary (a combination of 1s and 0s), and when you store numbers that way, they may not exactly equal the number in decimal. Here's an article that explains more:

Floating-point arithmetic may give inaccurate result in Excel - Microsoft 365 Apps

Discusses that floating-point arithmetic may give inaccurate results in Excel.

docs.microsoft.com

One way around it is to use ROUND when doing comparisons. You can also use the Precision as Displayed option, although that has some issues too.