How do I calculate standard deviation in Excel to use with error bars?

To calculate standard deviation in Excel, you can use the `STDEV.S()` function for a sample, or `STDEV.P()` for an entire population. For example, if your data for a specific series is in cells B2 to B10, you would enter `=STDEV.S(B2:B10)` in an empty cell to get the standard deviation value.