This procedure is provided for compatibility with earlier versions of Word. Use this procedure to insert an equation or expression into a document that you want to share with earlier versions of Word. If you do not need to share the file with earlier versions of Word, use the Document Elements tab to create mathematical equations or expressions. For more information, see Insert or edit an equation or expression.

Click where you want to insert an equation.

On the Insert menu, click Object.

In the Object type box, click Microsoft Equation, and then click OK.

To build the equation, select templates and symbols from the Equation toolbar and type variables and numbers.
Tip: For assistance editing an equation, click the Equation Editor Help menu, and then click Equation Editor Help.

To insert your equation, on the Equation Editor menu, click Quit Equation Editor.
See also
Edit an equation that was created in an earlier version of Word