Net Present Value (NPV) Calculator
Should you invest in a project or business opportunity? NPV converts future cash flows into today's dollars to show whether the investment beats your required return rate.
Understanding Net Present Value
Net present value solves a fundamental investment question: is a dollar tomorrow worth a dollar today? The answer is always no. If you can earn 10% annually, $1 today becomes $1.10 next year. Working backward, $1 received next year is only worth about $0.91 today.
NPV applies this logic to entire projects. Take all the future cash flows an investment will generate, discount each one back to present value, then subtract the upfront cost. If the result is positive, the investment creates wealth. If negative, it destroys wealth even if the nominal returns look good.
Consider a $10,000 investment that returns $3,000, $4,000, and $5,000 over three years. The total nominal return is $12,000, a 20% gain. But at a 10% discount rate, those future dollars are worth less. The present value of that cash flow stream might only be $10,260, making the true gain just $260 or 2.6%. NPV reveals the real economics hiding behind raw cash flow totals.
NPV in Capital Budgeting
Businesses use NPV to choose between competing projects. A company with $1 million to invest might face three options: expand the factory, launch a new product, or acquire a competitor. Each has different costs, timelines, and risks. NPV provides a common yardstick to compare them.
The decision rule is simple: accept all projects with positive NPV at your required rate of return. If capital is limited, rank projects by NPV and choose the highest until money runs out. Some analysts prefer ranking by profitability index to account for project size, but the logic is identical.
NPV also handles terminal values easily. If you plan to sell an asset at the end of the analysis period, treat the sale price as a cash flow in the final year. Buying rental property? The eventual resale value is just another cash flow to discount alongside the rental income.
Common NPV Mistakes
The most frequent error is using the wrong discount rate. Your discount rate should reflect both the time value of money and the risk of the cash flows. A guaranteed government bond might use 3%, while a speculative startup should use 20% or higher. Using too low a rate makes bad investments look good.
Another mistake is forgetting to include all cash flows. Maintenance costs, taxes, and eventual disposal expenses all matter. A solar panel installation might generate savings for 20 years, but panels degrade and inverters fail. Excluding replacement costs inflates the NPV.
Finally, NPV assumes you can reinvest cash flows at the discount rate. If you use a 15% rate but can only reinvest returns at 5%, your actual results will fall short of the NPV prediction. Be honest about your realistic reinvestment opportunities when setting the discount rate.
Frequently Asked Questions
What does a positive NPV mean?
A positive NPV means the investment generates more value than it costs, after accounting for the time value of money. It should be accepted. A negative NPV means the investment destroys value and should be rejected.
How do I choose the discount rate?
Use your required rate of return or cost of capital. For personal investments, this might be 8-12%. For businesses, use the weighted average cost of capital (WACC). Higher risk projects should use higher discount rates.
What is the profitability index?
The profitability index (PI) is the ratio of the present value of future cash flows to the initial investment. PI > 1.0 means positive NPV. It helps compare projects of different sizes.
Why discount future cash flows?
Money today is worth more than the same amount in the future because you can invest it and earn returns. Discounting adjusts future cash flows to reflect what they're worth in today's dollars.
What if my cash flows are uneven?
That's normal. Most real investments have irregular cash flows. This calculator handles different amounts each year. Just enter the expected cash flow for each period.