SUMIF scans through the range argument row by row, checking each cell against criteria. When it finds a match, it adds the corresponding cell from sum_range to a running total and then continues scanning. The range and sum_range do not need to be the same column — they just need to cover the same number of rows so that corresponding rows line up correctly. The criteria argument is flexible: text conditions must be in quotes, numeric conditions can be bare numbers or comparison strings like ">500", and wildcards work in text criteria using * and ?. When you need to compare against a value in another cell, concatenate the comparison operator with a reference: ">"&A1 means greater than whatever is in A1. Using full column references like B:B instead of B2:B100 means the formula automatically captures new rows added to the data without any formula updates. SUMIF only supports one condition — if you need two or more, use
SUMIFS instead which extends the same logic to multiple criteria pairs.