A cell in a Microsoft Excel spreadsheet can contain an equation that refers to the value of other cells in the spreadsheet. You can use an Excel equation to quickly find the sum of all the cells in a given row. If the value of any cell in the row changes, the cell containing the equation will automatically update to reflect the new sum.
Using a Shortcut
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Step 1
Click the cell in your Microsoft Excel document that you want to contain your equation, or highlight the cell using your keyboard's arrow keys.
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Step 2
Hold down the "Alt" key, and then press the "+" key. Alternatively, click the "Home" tab on the ribbon bar at the top of the window, and then press the "Sum" button. The "Sum" button is in the "Editing" section of the ribbon and is represented by the Greek letter sigma.
Step 3
Click the first cell you want to add in the row, and then drag the cursor to the last cell you want to add.
Step 4
Press the "Enter" key.
Manually Typing an Equation
Step 1
Click the Excel cell where you want to place your equation, or highlight the cell using your keyboard's arrow keys.
Step 2
Type "=SUM(" to begin your equation.
Step 3
Type the address of the first cell you want to add, and then press the "." key twice. The address of a cell consists of its column letter followed by its row number.
Step 4
Type the address of the last cell you want to add, and then type the ")" character.
Step 5
Press the "Enter" key.