Why a dollar tomorrow is worth less than a dollar today
Net present value answers the single most important question in investing: is this project 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? That discount exists because today's money can be invested to earn a return, and because future money carries risk and inflation.
NPV works by discounting every future cash flow back to today using a chosen rate, summing those present values, and subtracting the initial investment. If the result is positive, the project earns more than your required return; if it is negative, your money is better deployed elsewhere.
This calculator does the discounting for each period so you can compare projects on an apples-to-apples, present-value basis.
The NPV rule and what the discount rate means
The decision rule is simple once the math is done:
| NPV result | Interpretation |
| --- | --- |
| positive | The project earns more than the discount rate; accept it |
| zero | The project exactly meets your required return |
| negative | The project earns less than required; reject it |
The discount rate is the lever that changes everything. It represents your required rate of return or cost of capital, and a higher rate punishes cash flows that arrive far in the future. A project that looks great at an 8% discount rate can turn negative at 15%, which is why the rate must reflect the real risk of the cash flows.
How to use the calculator
Enter the initial investment as the amount you pay up front.
Add the expected cash flow for each future period (year or month).
Set the discount rate that reflects your required return or cost of capital.
Read the NPV; positive means the project clears your hurdle rate.
Choosing a defensible discount rate
The output is only as good as the rate you feed it, so choose it deliberately. For a company, the weighted average cost of capital is the standard starting point. For a personal investment, use the return you could reliably earn elsewhere — a diversified index fund's long-run average is a common benchmark. Run the calculation at two or three rates to see how sensitive the decision is; a project whose NPV flips from positive to negative across a small rate change is a fragile bet.
Pair NPV with the internal rate of return for a fuller picture: NPV tells you the dollar value created, while IRR tells you the percentage return.
Common mistakes
Forgetting to enter the initial investment as an outflow, which inflates NPV.
Using a discount rate that ignores the project's real risk, making risky projects look safe.
Mixing time periods — annual cash flows with a monthly rate, or vice versa.
Treating a small positive NPV as a strong signal when it is within the margin of your estimates.
Where NPV is used
Capital budgeting decisions on whether to fund equipment, expansion, or a new product.
Comparing two investments with different timing of returns on a single scale.
Valuing rental property or a business by discounting its projected cash flows.
Deciding whether to buy now or wait, by valuing the future savings.
Frequently asked questions
Q: What does a positive NPV mean?
A: The project's discounted cash flows exceed its cost, so it earns more than your required return and creates value.
Q: How is NPV different from IRR?
A: NPV is the dollar value created at a chosen discount rate; IRR is the discount rate at which NPV equals zero. Use them together.
Q: What discount rate should I use?
A: Your cost of capital or the return available on a comparable-risk alternative. Test a range to gauge sensitivity.
Q: Are my numbers stored?
A: No. The calculation runs locally in your browser.
Calculate NPV now
Open the NPV Calculator. For related analysis, compute the IRR, the ROI, or a Payback Period.
