Goal Seek answers the backwards question a spreadsheet cannot: you already know what the answer should
be, and you need to know what to put in.

WHERE TO FIND IT AFTER INSTALLING
Goal Seek opens in the SIDE PANEL on the right of your spreadsheet, not in the Extensions menu.
Look for its icon in the narrow strip down the right edge; if that strip is hidden, click the
small arrow at the bottom-right corner to show it.

What interest rate makes this payment 1,500? What price makes this margin 30%? How many units do we
have to sell to break even? You name the cell with the formula, the number it must reach, and the one
cell it may change — and it searches until it lands.

HOW IT WORKS
• The panel opens already filled in from the cell you have selected, so you do not retype anything.
• It writes candidate values into the one cell you nominated, lets Google Sheets™ recalculate, reads
  the result, and closes in on your number.
• It tells you exactly what it cost: how many recalculations it needed and how many seconds it took.
  No silent spinner.
• One click puts the cell back the way it was.

BUILT AROUND WHAT THE OLD TOOL GOT WRONG
Google Sheets™ has no What-If Analysis in its menus, so this job has always fallen to add-ons — and
the reviews of the one most people found say the same four things. Each one is answered here.
• "SUPER slow — a simple loan calculation took over twenty seconds." Every attempt is a full
  recalculation on Google's servers, so the number of attempts IS the speed. This add-on brackets the
  answer and then uses Brent's method, which typically needs eight to twelve attempts instead of
  hundreds.
• "It doesn't auto-populate — I have to re-enter everything every time." The form opens from your
  current selection, and remembers what you typed last time.
• "It throws an error when the panel opens." Every card is built and tested against a strict simulation
  of the platform before release.
• "It often fails" with no explanation. Here every failure names its cause — the goal is unreachable,
  the target cell is an error, the formula steps rather than slides — and your sheet is put back
  exactly as it was.

IF YOU CAME LOOKING FOR SOLVER
A lot of people search for a solver when what they actually need is this. The difference is the number
of unknowns. Solver changes SEVERAL cells at once under a list of constraints — a production mix, a
schedule, a portfolio. Goal Seek changes ONE cell until one formula hits one number, which is the case
most people actually have:

  "I wanted the monthly payment to be $400 by changing the cell that contained the mortgage rate."

That is one input and one target, so it is goal seeking, not optimisation — and it lands in seconds
instead of grinding. If your problem really does have several variables and constraints, this add-on
is not the tool, and it will tell you so rather than pretend.

A GUARD THE OTHER ONE DOES NOT HAVE
Goal seeking has to overwrite the cell it changes. If you point it at a cell containing a formula, this
add-on refuses to start rather than destroy it — the same way Excel refuses.

WHAT IS FREE, FOREVER
The search itself, with no limit on how often you run it. The optional search range that keeps answers
sensible. The undo button. And the full explanation of every failure. Those are safety, and safety is
not for sale.

PRO ADDS CAPACITY, NOT CORRECTNESS — $29 a year or $69 once, per user
Run the same goal down a whole table of scenarios, and save the setups you reuse. The licence is for Goal Seek; a team licence
covers every add-on we publish.

ONE PERMISSION, AND NO SERVER
It asks for a single permission — "See, edit, create, and delete only the specific Google Sheets™
spreadsheet this application is used in." It cannot see your Google Drive™, your other files, your mail
or your contacts. Nothing from your file is ever sent anywhere: there is no database and no analytics. Without a licence key the add-on makes no network request at all; with a Pro licence it asks our licence server once a day whether that key is still active, sending only the key and a random identifier for the installation.

ONE THING IT CANNOT DO, SAID PLAINLY
It cannot give you a keyboard shortcut. Google Workspace™ add-ons are not allowed to bind keys — no
add-on can, whatever its listing claims. You open it from the side panel.

Google Sheets™, Google Drive™, Google Workspace™ and Google Apps Script™ are trademarks of Google LLC.