How do I apply the same formula to multiple cells in Excel?

To apply the same formula to multiple cells in Excel, you can use the fill handle or keyboard shortcuts. Here's how:

Using the Fill Handle

Select the Source Cell: First, select the cell containing the formula you want to copy.
Select Target Cells: Select the cell with the formula, along with the adjacent cells where you want to apply the same formula.
Use the Fill Handle: Look for the small square at the bottom-right corner of the selected cells (this is called the fill handle). Click on it and drag it to cover all the cells you want to apply the formula to, whether it's down, right, up, or left. Excel will automatically adjust cell references in the formula as needed.

Example: If cell A1 has the formula =B1*C1, dragging the fill handle down to A2, A3, and so on will change the formula to =B2*C2, =B3*C3, and so on respectively.

You can also use keyboard shortcuts to fill formulas:

Fill Down: To fill a formula down in a column, select the cell with the formula and the cells below it, then press Ctrl + D.
Fill Right: To fill a formula to the right in a row, select the cell with the formula and the cells to its right, then press Ctrl + R.

Relative References: By default, cell references in formulas are relative. When you copy a formula, Excel will adjust the row and column numbers based on the direction you are filling. For instance, if your formula is =A1+B1 and you drag this to the right, it will become =B1+C1 in the new cell.
Absolute References: If you need a reference to stay constant when you copy a formula, you must use absolute references, denoted by a dollar sign ($). For example, if your formula is =$A$1+B1, the A1 cell reference will not change when the formula is dragged. It will always refer to cell A1. However, the B1 reference will change to B2, B3, etc.
Mixed References: You can also have mixed references like $A1 or A$1 to fix either the column or row, respectively, while the other reference will remain relative.
Formulas with conditions: You can apply these methods even when formulas include complex conditions, IF functions, SUMIF functions etc. The relative and absolute references still apply as described above.

Here's a table summarizing the methods:

Method	Steps	Keyboard Shortcut	Description
Fill Handle	Select cell with formula, select target cells, drag the fill handle.	N/A	Drag the small square to copy the formula to adjacent cells.
Fill Down	Select cell with the formula, select cells below, then press Ctrl + D	Ctrl + D	Copies the formula down a column.
Fill Right	Select cell with the formula, select cells to the right, then press Ctrl + R	Ctrl + R	Copies the formula to the right in a row.

By understanding and using these methods, you can efficiently apply your formulas to many cells without having to rewrite them each time.