The reason for this could be that the "numbers" are actually text and therefore won't be included in any calculations. One way to get around this is to use the VALUE function which will turn any text which could be represented as a number into a number.
HTH,
Dax.
Are you describing rounding error? If so consider
using the Tools | Options... menu command to check
"Precision as displayed" on the dialog's
Calculation tab.
The problem is I have a spreadsheet that has to sun columns of figures and then use these figures to calculate pro rata.
When you auto sum the pro rata values they show aas the correct amount but when using the Tools, Options, Precision it is usually 1 out e.g. pro rata values 134.56 162.73 204.42 = 507.71 (which is the figure I require), but if you add them manually it = 507.72.