Excel BODMAS rule and the errors that can arise

One of the most common logic errors made in Excel is not using the BODMAS rule that applies to maths and is used within Excel. A recent error we found in a clients spreadsheet related to the incorrect useĀ of the Excel BODMAS rule.

BODMAS stands for Brackets Of Division Multiplication Addition Subtraction and tells you the order the you must prioritise the calculations. This is important to get the correct answer.

So imagine we are doing movement studies and have determined that an event takes 0.2 of an hour to go the one way and 0.1 of an hour to repeat the process on the return leg. If you want to see what the total return time is in minute we need to add these 2 together and multiple the answer by 60.

Below the answers you get depending on whether you put in the brackets or not.

0.2+0.1*60=6.2 minutes


(0.2+0.1)*60=18 minutes

In the first option, because we have no brackets, the BODMAS rule multiplies the 0.1 by 60 (BODMAS) and then adds the result to the 0.2 (BODMAS). This is clearly very wrong and results in a 67% error.

It is important to remember this when doing calculations in Excel.

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