INDIRECT

This formula takes a little time to set up, but once it's up and running it can save tons of time.
 Say you have multiple months for which you need to calculate data. Each months' data is on a separate sheet.












INDIRECT() allows you to reference a cell (containing the sheet name) which then points you to the correct sheet. Just set it up once and you can drag the formula without any manual formula changes. I used it nested in a COUNTIFS() statement, as follows:

=COUNTIFS(INDIRECT("'"&I$2&"'!"&"$K:$K"),">"&$H8,INDIRECT("'"&I$2&"'!"&"$K:$K"),"<"&$G10)

Learn more about it here: http://www.contextures.com/xlFunctions05.html

Ceiling

Ever need to round up to the multiple of a specific number?

Example: I need one full time employee for every 7 agents. But I can't hire 1/7th of an FTE. You could use min/max or IF statements, but =CEILING() is faster. Ceiling will round up to the next multiple of 7. So if I have 6 agents, there is 1 FTE, but if there are 8 agents, it is bumped to two.

Check it out here: https://exceljet.net/excel-functions/excel-ceiling-function