If you know the result of a formula but not the value of a specific variable on which the formula depends, you can use Goal Seek to adjust the variable to display the desired value. Goal Seek can only adjust one variable in a formula, so if a formula depends on more than one variable, you will need to decide which variable to adjust.
To use Goal Seek:
- On the DATA tab, in the Data Tools group, click the What-If-Analysis command:
- Click Goal Seek:
- In the Goal Seek dialog box:
- In the Set cell box, enter the cell for which you know the result (if you selected this cell before clicking Goal Seek, then it is already filled in).
- In the To value box, enter the value for the cell above.
- In the By changing cell box, enter the cell to adjust in order to obtain the value. (Remember, this cell must be related via a formula to the cell above or else changing one won't impact the other.)
- Click OK:
- In the Goal Seek Status dialog box, after the calculation has completed, click OK to accept the change or Cancel to reject it: