How many rows are in one Microsoft Excel sheet?

There are 2²⁰=1,048,576 rows, and 2¹⁴=16,384 columns in an an Excel worksheet, at least since Excel 2007.

To find out how many rows, you can open an empty worksheet, and press CTRL-Down-Arrow key combination on your keyboard. The cursor will move all the way to the bottom row of the sheet. Look for the row number on the left.

To find out how many columns, you can press CTRL-Right-Arrow key combination in an empty worksheet, and you will find yourself at column XFD. So how many columns is that?

There are 26 columns labeled A through Z, and then there are 26²=676 columns labeled AA through AZ. Then start the columns with 3-letter names. Treat AAA like 000 in base 26 arithmetic. Treat A as the 0 digit, and Z as the 25 digit in base 26 numerals. So X is the 23 digit, F is the 5 digit, and D is the 3 digit, and XFD is the base-26 for 23×26²+5×26+3×1=15,681 . So the three-letter column names run from 0 to 15,681, so there are 15,682 of them.

So altogether there are 26 + 676 + 15,682 = 16,384 columns.