Turn a one-off cost, a running cost and a benefit into the four numbers a finance reviewer asks for — net present value, ROI, payback and break-even benefit — and see how much of the benefit can fail to arrive before the case stops paying for itself.
Last updated: 9 November 2026 · Runs in your browser · No sign-up · No email
A business case calculator converts the numbers a sponsor already knows into the figures a finance reviewer will ask for. You put in what the investment costs, what it costs to run, and what it is expected to return. The calculator turns that into a net present value at your organisation’s hurdle rate, an ROI, a payback period and a year-by-year cash flow.
Most calculators stop at the headline. In practice, the number that decides the conversation is a different one: how far can the benefit fall before the investment stops being worth doing? This calculator reports that as a break-even benefit and as a percentage of headroom, because a case that survives a 30% shortfall is a materially different proposition from one that needs every assumption to land exactly as planned.
What it cannot do is make the inputs true. Every figure below is a model, not a forecast, and the credibility of the result comes from where the benefit number came from — a contract, an invoice, a headcount, a benchmark the buyer already accepts.
Implementation, integration, migration, hardware and training — everything spent before go-live.
Licences, support, hosting and the internal effort to run it. Leave at zero if the benefit is already net.
Cost savings plus the gross margin on attributable revenue — never top-line revenue. Enter the gross figure; the haircut is applied below.
The share of the modelled benefit that actually lands in the accounts. 60–75% is a common working range; 100% is the number a finance reviewer discounts on sight.
Bridge from go-live to the full run rate, straight-line. 0 assumes the benefit lands in month one.
How many years the sponsor is asking to be judged over.
The rate finance applies to any other use of the same money. If you do not know it, ask them — 8–12% is a fair working range.
Discounted at 10%, the case is worth $116,826 more than it costs — $490,000 of benefit against $330,000 of cost.
Undiscounted, over the horizon
Discounted: 19.8 months
The case returns exactly its own cost while the benefit stays above $173,678 a year. That is 28% of headroom below the $240,000 you entered.
Quote this number next to the headline. A case that survives a 30% shortfall is a different proposition from one that needs every assumption to land.
| Year | Benefit | Cost | Net | Discounted |
|---|---|---|---|---|
| 0 | — | $150,000 | −$150,000 | −$150,000 |
| 1 | $154,000 | $60,000 | $94,000 | $88,752 |
| 2 | $168,000 | $60,000 | $108,000 | $93,277 |
| 3 | $168,000 | $60,000 | $108,000 | $84,797 |
Month 0 is not discounted. Recurring cost is spread evenly; the benefit ramps straight-line over 3 months and is recognised at 70% — $168,000 a year at full rate.
The calculator builds a monthly cash flow and reads every figure from it. The one-off cost is spent at month 0 and is not discounted. Recurring cost is divided by twelve and charged every month. The benefit is reduced by your realisation rate, then ramped straight-line from zero to that rate over the ramp months, so a six-month ramp credits one sixth of the monthly benefit in month one and the full amount from month six onwards.
At the calculator’s default settings — a $150,000 one-off cost, $60,000 a year to run, $240,000 of gross annual benefit recognised at 70%, a three-month ramp, a three-year horizon and a 10% discount rate — the recognised benefit is $168,000 a year. Over three years that is $490,000 of total benefit against $330,000 of total cost ($150,000 plus three years at $60,000), so the undiscounted ROI is 48% and the net benefit is $160,000.
Discounting each month at 10% gives a net present value of about $116,826, payback in 18.2 months undiscounted and 19.8 months discounted. The break-even benefit is $173,678 a year — so the gross benefit can fall 27.6% from $240,000 before the case is worth exactly what it costs. Set the inputs to those values and you will see the same figures; the arithmetic is deliberately simple enough to reproduce by hand.
Two conventions are worth stating because they change the answer. Money is discounted monthly at the annual rate rather than annually, which is slightly more conservative than discounting year-end totals. And the one-off cost sits at month 0, undiscounted, which is the convention of a spreadsheet’s NPV function with the initial investment entered separately.
Cases rarely fail on the arithmetic. They fail because one assumption cannot be defended. The three that come up most often are benefits counted at 100%, benefits assumed to arrive immediately, and revenue counted at the top line instead of the margin on it. Each of the first two has a control on this page — the realisation rate and the ramp — and the third is a matter of entering margin in the benefit field rather than revenue.
The presentation problem is separate. A single large number invites a single large challenge. A number presented with its break-even beside it moves the conversation from “do we believe this?” to “what would have to be true for this not to work?”, which is a question the sponsor can answer.
None of this rescues an input that was invented. If the benefit cannot be traced to a cost line, a contract or a measure the buyer already reports, no realisation rate will make it credible — it will simply take longer to be rejected.
It is built for anyone who has to put a number in front of someone else’s finance team. On the buying side that is a sponsor or project manager assembling a funding request, a PMO analyst building the options paper, or a finance business partner testing a proposal that has landed on their desk. On the selling side it is an account executive or value engineer building the case for a purchase the buyer will have to defend internally.
It is less useful at the very start of a conversation, when the honest answer is that nobody knows the benefit yet. At that point the useful work is finding the cost line the investment changes; the calculator will still be here once that number exists.
A calculator gives you a number; a committee approves a case. The gap between the two is sourcing, alternatives and a narrative that says what happens if nothing is done. Once you have a defensible figure, the next steps are to write the case down in a structure a reviewer expects, to test it against the assumptions finance will challenge, and to have a conservative scenario ready beside the expected one.
Start with the free business case template for the seven fields a reviewer looks for, then run the number through the business case readiness diagnostic and the ROI defensibility checker before anyone sees it. For category-specific models, the SaaS ROI calculator and the cybersecurity ROI calculator go deeper on those two purchases. The CFO-proof business case guide covers the structure, and the 2026 research on B2B business cases covers what buyers and reviewers say they are actually asked for.
ValueNova is an AI value-engineering platform that helps B2B sales teams produce repeatable, sourced business cases — taking a number like this one and wrapping it in the assumptions, scenarios and traceability that finance signs off on.
Common questions about the business case calculator, the formulas behind it, and how to make the result survive a finance review.
It builds a monthly cash flow from seven inputs: the one-off cost, the recurring annual cost, the gross annual benefit, the share of that benefit you expect to realise, the months it takes to reach full benefit, the number of years you are assessing, and the discount rate finance applies. From that cash flow it reports four numbers: net present value, ROI, payback period and the break-even benefit — the gross annual benefit at which the case is worth exactly what it costs. Everything is computed in your browser as you type.
The break-even benefit is the gross annual benefit at which net present value is zero, holding every other input fixed. It answers the question a finance reviewer actually asks: how wrong can this case be and still be worth doing? A case with a large ROI that needs 95% of its benefit to arrive is more fragile than a smaller ROI with 40% headroom. Quoting the break-even figure beside the headline is what separates a modelled number from a defended one.
A realisation rate is the share of the modelled benefit you expect to land in the accounts. If a project is forecast to save 1,000 hours, not all of that time becomes new output — some is absorbed as slack, and some savings are never taken out of the cost base. Applying a realisation rate makes the case smaller and more credible. There is no universal right value: 60–75% is a common working range for productivity benefits, and higher figures are defensible only when the saving is a contract or headcount the buyer has already committed to remove.
The rate your finance function applies to any other use of the same money — the hurdle rate or weighted average cost of capital. It is a policy number, not a judgement call for the person writing the case, so ask finance for it and record where it came from. If nobody can tell you, model the case at 8% and at 12% and show both: if the conclusion changes between those two rates, the decision does not depend on the maths, it depends on the appetite for risk.
It depends on the horizon and on how much of the money is at risk, so treat any single threshold with suspicion. Payback answers "how long is the money exposed before it comes back", not "is this worth doing" — that is what net present value answers. A short payback with a small total return can be a worse decision than a longer payback on a much larger return. The useful comparison is against the alternatives: doing nothing, a smaller pilot, or a different way of achieving the same outcome.
Use this calculator to settle the shape of the case in a few minutes: whether the outlay is recoverable inside the horizon, how much headroom the benefit has, and which of the inputs the answer is most sensitive to. Use a spreadsheet when you need to model several options side by side, tax, depreciation or an uneven cost profile. The arithmetic here is deliberately simple and stated in full on this page, so you can reproduce every figure by hand or in a spreadsheet and check the tool rather than trust it.
No. The calculation runs entirely in your browser. Nothing you type is sent to a server, stored, or attached to an enquiry, and there is no form to complete before you see a result. You can model a case, reset, and re-run it as often as you need.
The template, the diagnostic and the defensibility check that turn a modelled number into a case finance will sign.
Discover the gaps in your business case before the CFO does. Get your readiness score, see exactly where you're vulnerable, and know what to fix.
Stress-test your ROI before finance does. Identify weak assumptions, missing scenarios, and hidden dependencies that could sink your deal.
Seven fields in Word, Excel and Google Docs, with no email form in the way. A starting point for the case a buyer will actually review — plus the five parts of the job a template cannot do on its own.