Try Goal Seek
You know the answer you want — break even at $50,000 — but not the input that gets you there. Goal Seek works backward: tell Excel the result you want, and it finds the input that produces it. No algebra, no guessing — just the number.
TL;DR / Quick Fix
Quick fix: put your formula in a cell, then open Data, What-If Analysis, Goal Seek. Set the formula cell, type your target value, and pick the input cell Excel may change. Click OK and Excel iterates to the answer. It changes one input — multi-variable problems need Solver instead.
Follow these steps
- Set up the formula first. Build the model normally — price times quantity, loan payment formula, whatever. Goal Seek needs a live formula to work backward from.
- Open Goal Seek. Go to Data, What-If Analysis, Goal Seek. Three fields: the formula cell, your target value, and the input cell to change.
- Point at the input cell. Tell Excel which single cell it may adjust. Everything else stays fixed — Goal Seek solves one variable only.
- Run it and read the result. Click OK. Excel iterates and reports the input value that hits your target — plus whether it converged.
- Sanity-check the answer. A mathematically valid answer can be nonsense in reality — negative prices, fractional people. Reality-check before using it.
- Know when to upgrade to Solver. Multiple variables or constraints need Solver, Excel's bigger what-if tool. Goal Seek is the quick single-variable version.
What NOT to do
- Do not use it on a broken formula. Goal Seek on an erroring cell just errors differently — fix the model first.
- Do not accept absurd answers blindly. Convergence does not mean sense — validate against reality.
- Do not forget it overwrites the input. Copy the original value aside first; Goal Seek does not keep history.
- Do not expect multiple variables. One changing cell is the limit — that is what Solver is for.
Frequently asked questions
What is the difference between Goal Seek and Solver?
Goal Seek adjusts one input to hit one target. Solver handles many variables with constraints — the heavyweight version.
Why does it say it cannot find a solution?
No input produces your target — the target may be impossible, or the formula may not respond to that input.
Can I undo Goal Seek?
Yes, immediately with Ctrl+Z. But save a copy of the original input first for safety.