The easiest way to multiply two numbers in Google Spreadsheets is to create a formula in a worksheet cell.
Important points to remember about Google Spreadsheet formulas:
 Formulas always begin with the equal sign ( = );
 The equal sign always goes in the cell where you want the answer to go;
 The multiplication operator is the asterisk ( * );
 The formula is completed by pressing the Enter key on the keyboard.
You may hear the terms formula and function used interchangeably, but they are not the same. A formula is an expression used to calculate the value of a cell. But a function in Google Sheets is a predefined formula that helps make more complex calculations without a great deal of effort
Try It Out
The best way to see how multiplication works in Google Sheets is to try it out yourself.

Open up Google Sheets, and click in a cell to start typing.

Enter the equal sign ( = ).

Then, type a number.

Enter the asterisk( * ) to signify multiplication.

Type in the second number to multiply.

Press Enter to see the result.
Using Cell References in Formulas
Even though entering numbers directly into a formula works. it is not the best way to create formulas.
The best way is to use cell references. Cell references are essentially variables, holding whichever data is in the cells they're referencing, hence the name. They allow you to change data within cells on the fly, and copy formulas across columns and rows to multiple different sets of data dynamically.
Cell references are a combination of the vertical column letter and the horizontal row number with the column letter always written first — such as A1, D65, or Z987.
Cell Reference Advantages
Cell references are used to identify the location of the data used in a formula. The program reads the cell references and then plugs in the data in those cells into the appropriate place in the formula.
By using cell references rather than the actual data in a formula  later, if it becomes necessary to change the data, it is a simple matter of replacing the data in the cells rather than rewriting the formula.
Normally, the results of the formula will update automatically once the data changes.
Multiplication Formula Example
Working with cell references isn't much different than working with regular numbers. Start with an equal sign. Enter the reference the first cell, say A2. Type in an asterisk. Follow that with the second reference. If you're multiplying A2 and B2 in cell C2, the finished formula in cell C2 will be:
=A2*B2
Entering the Formula

Start by entering your data. Create two columns, each with a few numbers in it. Assuming you labeled your columns, this guide will begin work multiplying the data in A2 and B2 in cell C2.

Select cell C2 to make it the active cell — this is where the results of the formula will be displayed.

Type an equal sign (=) into cell C2.

Select cell A2 with the mouse pointer to enter that cell reference into the formula. You can also type A2, if you prefer.

Type an asterisk symbol ( * ) after A2.

Select cell B2 with the mouse pointer to enter that cell reference. Once again, you can always type it too.

Press the Enter key on the keyboard to complete the formula.

The answer should be present in cell C2.

Even though the answer is displayed in cell C2, selecting that cell will show the actual formula = A2 * B2 in the formula bar above the worksheet.
Changing the Formula Data
To test the value of using cell references in a formula:
 Change the number in cell A2 and press the Enter key on the keyboard.
The answer in cell C2 should automatically update to reflect the change in data in cell A2.
Changing the Formula
If it becomes necessary to correct or change a formula, two of the best options are:
 Double click on the formula in the worksheet to place Google Spreadsheets in Edit mode and then make changes to the formula — works best for minor changes.
 Click once on the cell containing the formula and rewrite the entire formula — best for major changes.
Multiplying Across Multiple Rows
Because you're working with cell references, you can copy your formula across multiple cells to apply it to multiple rows at once.

Working in the example from before, select the C2 cell that has your formula.

Hold Ctrl/Command, and press C to copy the data in the cell.

Click and drag to highlight the other cells in the same C column as the formula.

Hold Ctrl/Command, and press V to paste the formula in the highlighted cells.

The highlighted cells will immediately fill in with multiplication results from the formula.

Select one of the results cells, and you'll see that the formula in the cell correctly references the corresponding cells in columns A and B. That's because Google Sheets will automatically update to reference the correct row when pasting a formula.