Excel "=SUM" formula does not add up numbers correctly

If multiplying by 1 is a remedy, the data type of the "numbers" is text.  You must use ISTEXT to discern that.  The cell format and the visual appearance are misleading.

But it is possible that the cell format is also Text -- or it was Text when you entered the data.  Simply changing the cell format to General or another numeric format later is not sufficient.  You must also "re-enter" the data:  select the cell and press f2, then Enter.

Another option, which I've found to be more versatile: the value() function. It can usually be added without much effort, and without side effects.

example: change from '7' to '=value(7)'

I have Microsoft office 365 - Excel is not adding certain cells correctly

e.g. - say - =sum(i43:i59) = should be £32000 - Excel is adding it as £43000

Found that it is including cells i63-i72 - tried deleting these - still ads wrongly

Ronald wrote:

I have Microsoft office 365 - Excel is not adding certain cells correctly[.] e.g. - say - =sum(i43:i59) = should be £32000 - Excel is adding it as £43000[.] Found that it is including cells i63-i72

If you wrote I43:I59 as shown, it is not including I63:I72.

(Unless you mean that some values in I43:I59 are the same as some values in I63:I72, either by coincidence or by design.)

Two common reasons why the SUM might be wrong.

1. The workbook is in Manual calculation mode.  If you modify some of the cells in I43:I59, the changes will not be reflected in the result of the SUM formula.  Change to Automatic calculation.  Or just press f9.
2. Some of the values in I43:I59 are text, even if they appear to be numbers.  To confirm, enter the formula

=ISTEXT(I43) into J43 and copy down through J59.  It is not sufficient to look at the cell format; we can enter text into a cell with a numeric format.  The remedy depends on the content of I43:I59.

If you cannot correct the problem yourself, I suggest that you upload an example Excel file (redacted) that duplicates the problem to a file-sharing website (e.g. box.net/files), and post the public/share URL in a response here.  (Actually, you should start your own question, not piggyback someone else's.)  Test the URL first, being careful to log out of the file-sharing website.

All of a sudden, I find that spreadsheets I have been using for over a decade no longer calculate simple math correctly. Simple math! I have a column of numbers that I add up using =sum(..) function, which has been the same for decades. i started noticing bogus output a few weeks ago in one spreadsheet and have been scratching my head over it.  Now, when I change the numbers in the column being added, the output cell remains the same! WTF???? I thought I had a buggy spreadsheet or maybe a virus. Each time I wanted to do the calculation, I had to clear the output cell and reenter the function.  Today, I saw the same behavior in another spreadsheet that I have used for years and years. So I called Microsoft.  Those idiots batted me around between support "professionals" for a long while and I did some searching while I was on hold until I found your post, checked the settings, and surprise surprise surpise - you are correct. It was set to "manual" instead of "automatic"! But the question is, when was this "feature" added, and the bigger question is who the f would ever think of such a stupid idea and set it as the default without warning the entire world that their spreadsheets would no longer perform basic math???? my God. I am at a loss. A loss! How many errors have I been putting out to my business partners with my spreadsheet output and for how f-ing long? I simply cannot imagine any purpose for setting it to "manual". That is why we use spreadsheets! To quickly perform mathematical functions. If I wanted to do the work manually, I'd use a goddam adding machine for christsakes. What idiot though of this and when did Microsoft(brains) foist this upon us? I certainly never changed this setting in Excel and never heard of it before, nor would I ever think there was a want or a need out there to manually calculate data in a spreadsheet! Has the entire world been taken over by idiots? Has Microsoft been infected by morons? Or have I been unknowingly transported into a parallel dimension of idiots when before I lived in one where a) no one with even a high school education would even think of such a "feature" and b) Donald Trump was just a bankrupt failed businessman, not president of the US. Please, please tell me how I can get back to the other dimension where at least these two elements of my new reality do not exist. Please!