This page gives you five Gemini prompts for ROI calculations. Each one turns numbers you already have into a payback figure and a short explanation you can defend in a meeting. Copy a prompt, swap the bracketed inputs, paste.
Where ROI math usually falls apart
- You mix one-time costs with recurring costs on the same line, so the total is a number nobody can interpret.
- You present a single ROI figure as fact instead of a range tied to an assumption.
- You skip the baseline — what happens if you do nothing — so the result has nothing to sit against.
Five prompts that fix it
1. Sort the cost inputs
Here are my project costs: [paste cost list]. Split them into one-time costs, recurring monthly costs, and indirect costs. For each line, say whether it should be annualized or counted once, and flag anything ambiguous. Do not guess any figure I did not give you.What it does: Stops the most common error — a setup fee and a subscription merged into one meaningless total.
How to use: Paste your [cost list] as a bullet list, then answer the flagged lines before you continue.
2. Build the calculation step by step
I am evaluating [initiative name]. Total investment is [investment amount] over [time horizon]. Expected annual benefit is [annual benefit]. Build the ROI calculation step by step, show the formula you used, and return the result plus the payback period in months.What it does: Puts the formula next to the math so you can check the arithmetic instead of trusting it.
How to use: Replace [initiative name], [investment amount], [time horizon], and [annual benefit]. Keep every figure in the same currency.
3. Turn one number into a range
Using [investment amount] and [annual benefit], calculate ROI for three cases: conservative, expected, and optimistic. For each case, name the single assumption that changed. Present the three results in a small table.What it does: Converts one fragile figure into a range you can actually stand behind.
How to use: Set your own [annual benefit] for each case, or let the prompt propose the swing and then adjust it.
4. Compare against doing nothing
I am weighing [option A] against [option B] and against not investing at all. Here are the figures: [paste figures]. Calculate the incremental ROI of each option against the do-nothing baseline, and tell me which option wins on payback time.What it does: Gives the result a baseline, which is what a decision-maker actually asks for.
How to use: Replace [option A] and [option B], then paste both sets of [figures] in the same format.
5. Write the one-paragraph justification
Here is my ROI result: [paste result and assumptions]. Write one paragraph that states the result, names the assumption it is most sensitive to, and gives the weakest part of the estimate. Keep it under 90 words and do not add any figure I did not provide.What it does: Turns a spreadsheet into a sentence you can say out loud when someone pushes back.
How to use: Paste your [result and assumptions] from the earlier prompts. Read it once and cut anything that sounds like filler.
Weak ask vs better ask
| Weak ask | Better ask |
|---|---|
| Is this investment a good idea? | Calculate ROI for a conservative, expected, and optimistic case, and name the assumption each one depends on. |
| What’s the ROI? | Given [investment amount] over [time horizon] and [annual benefit], show the formula, the result, and the payback period in months. |
| Make the numbers look better. | Show which single input moves the ROI the most, so I can decide whether to defend it or fix it. |
Keep going
- Browse the Data & Analysis prompt library
- 5 ChatGPT prompts for data analysis plans
- 5 Claude prompts for chart critiques
- 5 Gemini prompts for Goal Seek
Take what works here and paste it straight into your tool of choice.