The easiest way to multiply two numbers in Google Sheets is to create a formula in a worksheet cell.
How to Work With Formulas In Google Sheets
Here are some important points to remember about Google Sheets formulas:
 Formulas begin with the equal sign ( = ).
 The equal sign goes in the cell where you want the answer to appear.
 The multiplication operator is the asterisk ( * ).
 The formula is completed by pressing the Enter key on the keyboard.
The terms formula and function are used interchangeably but are not the same. A formula is an expression that calculates the value of a cell. A function in Google Sheets is a predefined formula that makes complex calculations.
Multiply Numbers in Google Sheets
The best way to see how multiplication works in Google Sheets is to try it out.

Open Google Sheets, and select a cell.

Enter the equal sign ( = ).

Type a number.

Enter the asterisk ( * ) to signify multiplication.

Type the second number.

Press Enter to see the result.
Use Cell References in Formulas
Even though entering numbers directly into a formula works, it's not the best way to create formulas. The best way is to use cell references.
Cell references are variables that hold the data in the cells they reference. Use cell references to change data within cells on the fly, and to 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, for example, A1, D65, or Z987.
Cell Reference Advantages
Cell references identify the location of the data used in a formula. The program reads the cell references and then inserts the data in those cells into the appropriate place in the formula.
Using cell references rather than the actual data in a formula has benefits. Later, if the data needs to be changed, replace the data in the cells rather than rewrite the formula. The results of the formula update automatically when 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 to the first cell, type an asterisk, then follow that with the second reference. To multiply A2 and B2 in cell C2, the finished formula in cell C2 is:
=A2*B2
To enter a multiplication formula:

Enter the data.
To follow along with this tutorial, enter the data shown in the image below. Your worksheet doesn't need to be formatted exactly the same, but the numbers should be in the same cells as the example.

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

Type an equal sign (=).

Select cell A2 to enter that cell reference into the formula. Or, type A2, if you prefer.

Type an asterisk symbol ( * ).

Select cell B2 to enter that cell reference.

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

The answer appears in cell C2.

Select cell C2 to display the formula =A2*B2 in the formula bar above the worksheet.
Change 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. The answer in cell C2 automatically updates to reflect the change in data in cell A2.
Change the Formula
If it becomes necessary to correct or change a formula, two of the best options are:
 Doubleclick the formula in the worksheet to place Google Sheets in Edit mode, then make changes to the formula. This works best for minor changes.
 Select the cell containing the formula and rewrite the formula. This is best for major changes.
Multiply Across Multiple Rows
When you work with cell references, you can copy a formula across multiple cells to apply it to multiple rows at once.

Select the cell that contains the formula. In this example, select cell C2.

Press Ctrl+C on Windows or Command+C on Mac to copy the data in the cell.

Hold the handle (located in the lowerright corner of the selected cell) and drag to highlight the other cells in the same column as the formula (column C in this example).

Press Ctrl+V on Windows or Command+V on Mac to paste the formula in the highlighted cells.

The highlighted cells fill with multiplication results from the formula.

Select one of the results cells to make sure the formula in the cell correctly references the corresponding cells in columns A and B. Google Sheets automatically updates to reference the correct row when pasting a formula.