Every business owner has a decision they still argue with themselves about. The hire that took too long. The price increase that came a year late. The product line that should have been killed after month three.
Most of us never go back and score those decisions. We carry a vague feeling that we were right, or wrong, and move on. A spreadsheet can fix that.
The idea: a business decision calculator that lets you re-evaluate the ROI of past decisions using what you know now. It is one of the 100 business ideas in Google Sheets I put together, and it is one of the few that is as useful for the person building it as for the person buying it.
The idea
Have you ever wanted to go back in time and see whether the decisions you made were the right ones or the wrong ones? Build a calculator that does exactly that.
The core is simple. You record a decision, what you expected it to cost, what you expected it to return, and when you expected the return to show up. Later, you fill in what actually happened. The sheet compares the two and tells you how far off you were, in which direction, and by how much.
Ray Dalio talks about having this kind of tool in his book Principles. He treats decisions as bets, records them, and reviews the results systematically. That habit is worth a lot, and almost nobody does it because there is no easy place to write it down. A Google Sheet is that place.
You do not have to limit this to your own decisions either. Make it a mock business modeled on real companies. Give the user a few input fields, let them make decisions along the way (raise prices, hire, expand, cut a product), and show whether they would have gotten similar, better, or worse results than the people actually running the business at the time.
That second version turns the calculator into something closer to a game or a training tool. Founders learn by making choices and seeing consequences. Wrapping that in a sheet means the feedback is instant and the numbers are transparent. There is no black box.
What makes this sellable is the framework, not the arithmetic. Anyone can subtract expected from actual. The value is in deciding which questions to ask before a decision, which ones to ask after, and how to score the gap so the pattern of your mistakes becomes visible. If someone learns they consistently overestimate speed and underestimate cost, that is worth more than the price of a template.
How to build it in Google Sheets
Keep it to four tabs. More than that and people stop filling it in.
- Decisions tab. One row per decision. Columns: Date, Decision, Category (hire, pricing, product, marketing, spend), Expected Cost, Expected Return, Expected Payback in months, Confidence (1 to 5), Actual Cost, Actual Return, Actual Payback, Review Date, Notes.
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Scoring tab. Pulls from Decisions and calculates Expected ROI, Actual ROI, the gap between them, and a hindsight score. Something like
=IFERROR((I2-H2)/H2, "")for actual ROI keeps the sheet clean while rows are still empty. - Patterns tab. Groups the results by category and confidence so the user can see where they tend to be right and where they tend to be wrong.
- Simulator tab (optional). The mock business. A handful of input cells drive a small profit and loss statement, and the user's choices change the outcome.
Features worth using:
- Data validation dropdowns for Category and Confidence, so the Patterns tab can group cleanly.
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QUERY on the Patterns tab.
=QUERY(Decisions!A:M, "select C, avg(I) where I is not null group by C", 1)gives you average actual return by category in one cell. - Conditional formatting on the gap column. Green when actual beat expected, red when it did not. People read color before they read numbers.
- Checkboxes for Reviewed, so the user can see which decisions still need a follow-up.
- Time-driven Apps Script trigger with MailApp to send a monthly reminder listing decisions whose review date has passed. This is what turns a template into a habit.
- Protected ranges on the formula columns, so nobody types over the scoring logic.
For the simulator, build the profit and loss with hard-coded numbers first, then swap them for input cells one at a time. It is much easier to debug that way.
Who pays for it, and how to sell it
Three buyers come to mind. Solo founders who make a lot of decisions alone and have nobody to review them with. Small leadership teams who want a shared record of the bets they have made. And coaches or consultants who want a tool to run with their clients.
What they are paying for is the structure and the honesty it forces. Nobody buys a subtraction formula. They buy a repeatable review process they would never build themselves.
Pricing: a one-time template works well here, priced around what you would pay for a good business book. If you build the simulator version with several mock businesses, charge more, or sell each scenario as an add-on. Coaches will pay extra for a version they can rebrand and hand to clients.
Deliver it on Gumroad as a link to a view-only sheet the buyer copies. Or use OnlySheets, which sells access to a Google Sheet and handles the sharing automatically when someone pays. That is especially useful if you plan to update the scenarios over time and want buyers to always have the latest version.
First 10 customers: score three of your own past decisions publicly. Write them up, show the sheet, show the gap, and be honest about where you were wrong. Post it where founders hang out. People who watch you do it will want to do it to themselves, and the sheet is right there.
Related ideas from the list
- Financial Modeling for Small Businesses, because the simulator tab is a small financial model with decisions as the inputs.
- Prioritization Frameworks, which helps the same buyer decide what to do before this sheet scores how it went.
- Niche Mental Models, since a decision log is where mental models get tested against reality.
Want the other 99? This is one idea from my list of 100 business ideas you can build in Google Sheets. Get all 100 business ideas as a free Google Sheet.
And if you want to learn how to package and sell spreadsheets, my course Selling Spreadsheets walks through exactly that.
