[header] How to compare data in excel [title] Highlight the first cell of a blank column. [step] When comparing two columns in a worksheet, you'll be outputting your results onto a blank column. Make sure you are starting on the same row as the two columns you're comparing. 
[substeps] For example, if the two columns you want to compare start on a2 and b2, highlight c2. [title] Type the comparison formula for the first row.