This is one of the most basic functions but one of the most used too. Counting and adding has been know since very early times. We have always been able to count and add, usually using our fingers.

Here are the pros why you should implement a SUM…

• It is easy to write
• It is easy to read and maintain
• It is shorter to write that using + signs
• You can sum cells, ranges, hard coded numbers, a combination of those
• It summarizes tons of numbers in a flash
• It consider negatives in the computations (it subtracts them)
• It automatically detects the above side contiguous cells and include them in the formula (AutoSUM)
• It automatically detects the left side contiguous cells and include them in the formula (AutoSUM)

Here are the cons why you should be careful when implement a SUM function…

• It lead to unnoticed errors
• Arguments that are error values or text that cannot be translated into numbers cause errors.

I really love the Excel SUM function. You won’t believe me if I say you that my first sum formulas was long chains of + signs and cell references. My early SUM formulas contained paragraphs of arguments. When I met this formula, my productivity changed for ever.