Goal Seek: Solve for an Input

All versionsWhat-If

You know the answer you want — what input gets you there? Goal Seek works backward through any formula: set a target result and let Excel find the input value that produces it.

Quick formula: Data → What-If Analysis → Goal Seek:

Set cell: [result] To value: [target] By changing: [input]

Excel iterates until the result cell hits your target, then writes the required input back into the changing cell.

The example

What score on the final (B3) gives an 80 average?

	A	B
1	Item	Value
2	Average target	80
3	Final needed	86

The formula

Goal Seek is a menu tool, not a formula — here are its three boxes:

Set cell: B5 (the average formula) To value: 80 By changing: B3 (the final exam score) // Excel finds B3 = 86

How it works

Goal Seek reverses a formula by trial and error:

Build the model so the result is a formula depending on the input you want to solve.
Open Data → What-If Analysis → Goal Seek.
Set the result cell, the target value, and the changing input cell, then OK.
Excel iterates to find the input that hits the target and writes it into the cell. Cancel to discard, OK to keep.

When algebra is exact, prefer a formula. Goal Seek is iterative (and only changes one cell). For a needed-average problem you can solve directly: =targetAvg*count − SUM(otherScores). Use Goal Seek when the relationship is too tangled to rearrange by hand.

Try it: interactive demo

Live demo

Scores so far + target average → needed final.

Scores (so far)

Target avg

Final needed:

Variations

Direct formula (exact)

When you can rearrange it:

=targetAvg*count - SUM(others)

Solve a break-even

Set profit to 0 by changing units.

Solve a loan payment

Set payment to a budget by changing price.

Pitfalls & errors

One input only. Goal Seek changes a single cell. For multiple inputs use Solver.

It overwrites the input. Goal Seek replaces the changing cell’s value — note the original first, or Cancel to keep it.

Iterative, not exact. Results may be off by a tiny amount; round if you need a clean figure.

Practice workbook

📊

Download the free Goal Seek: Solve for an Input practice workbook

A Goal Seek model with the exact-formula equivalent, plus 4 challenges with answers. No sign-up required.

Frequently asked questions

How do I use Goal Seek in Excel?

Data → What-If Analysis → Goal Seek. Set the result cell, the target value, and the input cell to change. Excel finds the input that hits the target.

Can Goal Seek change more than one input?

No — it changes only one cell. Use Solver for problems with multiple inputs or constraints.

When should I use a formula instead of Goal Seek?

When the relationship can be rearranged algebraically (like a needed average), a direct formula is exact and updates automatically; Goal Seek is for tangled models.

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Related formulas: Break-even point · One-variable data table · Target-profit pricing