You can sum cells across multiple sheets in Excel. This article presents steps for Adding single-cell values or Adding values in the range of cells.

Google Sheets offers many of the same features as Microsoft Excel. The SUMIF function allows you to quickly sum rows that meet certain criteria.

You can't use a SUM() function to sum a filtered list, unless you intend to evaluate hidden and unhidden values. Here's how to sum only the values that meet your filter's criteria.

I keep running into situations in Excel where I want to calculate a conditional sum, but my criterion is something along the lines of "Include cell B1 if cell A1 is a number, likewise B2 and A2 ...

You can use SUMIF in Google Sheets to add numbers together that are associated with a date range, specific text, or meet a numeric criterion.