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Business case ROI calculator

Every case is presented as one confident number and attacked with the same question: what if you only get half of it? This one answers that first. It gives you payback and NPV, and then the share of your projected benefit that actually has to land.

Your case

Implementation, migration, licences, the first invoice.
What it costs every month once it is live, including the people who run it.
Saved cost or new revenue, once the thing is fully working.
Nothing delivers at full rate on day one. Empty assumes it does.
Three years is what most committees expect. A longer one quietly flatters any case.
Your finance team may have a number for this. Ten percent is a common default.

What has to land

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Add the cost and the benefit

What gets asked about this number

A business case is defended, not discussed, and the people opposite you are usually bidding for the same money. These four come up whatever the case. Fill the calculator in and the ones drawn from your own figures join them, marked.

  1. What does doing nothing cost? Not zero: what is the price of carrying on as we are?

    Every case is implicitly a comparison, and the alternative is rarely free. A case that has priced the status quo is arguing about a difference; one that has not is arguing about a spend.

  2. Who owns the benefit, and will they carry it in their own numbers?

    A saving nobody has agreed to be measured on tends not to appear. The question separates a benefit somebody has signed up to from one that was estimated on their behalf.

  3. Is internal time in the cost, or only what leaves the building?

    The people who implement, run and support the thing are the most commonly omitted line, because their salaries are already being paid. Finance will notice.

  4. Which single assumption, if it turned out to be wrong, takes this to zero?

    Naming it first is what separates a case somebody has stress-tested from one they have only built. It is also the question that gets asked whether or not you raise it.

Why the break-even benefit beats the ROI figure

A return on investment is a single number resting on a forecast, and a forecast is the softest thing in any business case. Quote 240% and the room does not hear a return, it hears an estimate it is about to test. The next sentence is always some version of what if you only get half of that.

The break-even benefit answers it before it is asked. If the case clears at 58% of the projected upside, you are no longer defending an optimistic number. You are defending a floor, and the burden has quietly moved to whoever thinks you will capture less than that. It is the same figure, read from the other end, and it is a much harder thing to argue with.

Payback, and why the ramp changes it

Payback is the month the running total crosses zero, undiscounted, which is the convention almost everybody uses. What moves it more than anything is the ramp: the months it takes to get from nothing to the full benefit. Assuming full delivery in month one is the most common way a payback figure turns out to be fiction, and it is the second question a case gets asked after the sensitivity one.

NPV, and the discount rate

Money later is worth less than money now, and net present value is the arithmetic that says by how much. The rate is your organisation's, not ours: finance usually has one, and using theirs is the difference between a case that survives review and one that gets sent back. Ten percent a year is a common default when nobody will tell you.

The one-off cost is not discounted here, because it is paid today. Discounting money you are about to spend is the most common sign error in a hand-built NPV, and it makes every case look better than it is.

What this does not do

No IRR: it needs iteration, it is widely misunderstood, and no budget meeting has ever been won with it. No tax, no depreciation, no capitalisation: those are your finance team's, and the answer depends on your jurisdiction and your accounting policy. The benefit ramps linearly rather than following an adoption curve, which is a simplification and an honest one.

Terms on this page

Break-even benefit
The share of your projected benefit that has to be delivered before the case stops paying for itself. Above 100% means it does not pay back on these figures.
Payback period
How long until the running total turns positive. Quoted undiscounted, by convention.
NPV
Net present value: every future amount reduced to what it is worth today, then netted off against what you spend now.
Discount rate
The annual rate at which future money is written down. Usually set centrally by finance.
Ramp
The period between switching something on and getting the full benefit from it.

A number is only as good as your answer about it.

Flintroom is a rehearsal room. A panel of AI interrogators presses on your argument out loud, quotes your own deck back at you, and does not accept the first answer. Then a coach rebuilds the ones that came loose.

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