If you know the result you need from a formula, you can use the Goal Seek add-on to find the missing value needed to achieve it.
You can use the add-on to conduct break-even analysis, or determine subcomponent targets when modeling future outcomes. You can also modify parameters, like max iterations, tolerance and max execution time that Goal Seek uses to determine a solution or load previous calculations.

There are three components to configure:
- the target value 
- the changing cell (where the formula is)
- the output value to achieve

Learn more about the add-on on support.google.com/docs/answer/9506732.