NPV Calculator
Calculate Net Present Value of an investment to determine viability.
What this calculator does
Net present value asks whether a project is worth more than it costs, once you account for the fact that money arriving in the future is worth less than money in hand today. Each future cash flow is discounted back to the present and summed, then the initial investment is subtracted.
The result is a dollar figure. Positive means the project is expected to add value beyond your required rate of return; negative means it destroys value relative to the alternative. Unlike a payback period or a simple ROI, NPV takes timing seriously, which is what makes it the standard capital budgeting measure.
When to use it
NPV is the right tool whenever cash flows arrive over several years and their timing matters — buying equipment, launching a product line, acquiring a rental property, or choosing between two projects with different profiles. It is also the correct way to evaluate a lump sum offered today against payments spread over time.
It matters most when the decision is close. If a project is obviously good or obviously bad, no calculation is needed. When two options look similar on a spreadsheet of undiscounted totals, discounting is usually what separates them, and the separation can be large.
Understanding the inputs
The starting amount is your initial outlay, entered at time zero and not discounted. Annual return is the discount rate — the return you require given the risk, not the return you hope for. Getting this wrong is the most common source of a misleading NPV.
Years is the projection horizon. Be careful about extending it: forecasts beyond five years carry little real information, and a long horizon can make a marginal project look attractive purely on speculative later cash flows. The monthly addition field lets you model recurring contributions or costs across the period.
How is this calculated?
NPV = Σ [CFt / (1 + r)^t] − Initial Investment. Positive NPV = profitable investment.
A worked example
A business is considering equipment costing $250,000 that should generate $70,000 in additional after-tax cash flow annually for five years. The company's cost of capital is 9 percent.
The five-year annuity factor at 9 percent is 3.8897, so the present value of those cash flows is $272,276. Subtracting the $250,000 outlay gives an NPV of $22,276 — positive, so the project clears the hurdle. Undiscounted, the cash flows total $350,000, making the project look $100,000 better than it actually is.
Limitations and assumptions
NPV is only as good as the cash flow forecasts fed into it, and forecasts are opinions. The technique's mathematical rigor can lend false confidence to inputs that are essentially guesses, particularly for years three onward.
It assumes a single constant discount rate, that intermediate cash flows can be reinvested at that rate, and that the project runs to completion as planned. It ignores option value — the ability to abandon, expand, or delay. Past returns do not predict future ones, and this is not investment advice.
Common Questions
- What does net present value actually mean?
- It is the value today of every future cash flow a project generates, minus what it costs to start. A positive NPV means the project is expected to create wealth above your required return. A negative NPV means the capital is better deployed elsewhere, even if the project shows an accounting profit.
- What discount rate should I use?
- For a business, the weighted average cost of capital is the standard choice, since it represents the blended return debt and equity holders require. For a personal investment, use the return you could realistically get from the next best alternative. The rate must reflect the project's risk, not just prevailing interest rates.
- Why does the discount rate matter so much?
- Because it compounds against every future year. At 5 percent, a dollar received in ten years is worth 61 cents today. At 12 percent it is worth 32 cents. Long-dated projects are extremely sensitive to the rate, which is why sensitivity analysis across a range of rates is standard practice.
- Is a positive NPV always a green light?
- No. NPV assumes your cash flow forecasts are accurate, and forecasts for years four and five are usually optimistic guesses. It also ignores capital constraints, execution risk, and strategic value. Treat a positive NPV as necessary but not sufficient, and always test what happens if revenues come in twenty percent below plan.
- How does NPV differ from IRR?
- NPV gives an answer in dollars, IRR in a percentage. NPV requires you to state a discount rate; IRR derives one. Where they disagree — typically on projects of different sizes or with differently shaped cash flows — finance theory says follow NPV, because it measures the actual value created.
- Should I include the initial investment as year zero?
- Yes, as a negative cash flow at time zero, undiscounted, because you are spending it now. A common error is discounting the initial outlay by one year, which understates the cost and inflates the NPV. Cash flows arriving during year one are discounted once.
- How do I handle salvage or terminal value?
- Add it as a cash inflow in the final year alongside the operating cash flow for that year. For an ongoing business, terminal value is often calculated as the final year's cash flow divided by the discount rate minus the growth rate. It frequently dominates the total, so the assumptions behind it deserve scrutiny.
- Should cash flows be before or after tax?
- After tax, and discounted at an after-tax rate for consistency. Depreciation is not a cash flow but it shelters income from tax, so its effect enters through a lower tax payment rather than as a direct outflow. Mixing pre-tax cash flows with an after-tax discount rate produces a systematically inflated NPV.
- Does NPV account for inflation?
- Only if you are consistent. Either forecast nominal cash flows and discount at a nominal rate, or forecast real cash flows and discount at a real rate. Both are valid and give the same answer. Mixing them — real cash flows with a nominal discount rate — understates NPV substantially over long horizons.