Profitability Index Calculator

Background.

A project that costs $100,000 and pays back over the next five years is worth doing only if those future dollars, valued today, come to more than $100,000. The profitability index states that test as a ratio: the present value of the inflows divided by the investment. Above 1, the project earns more than the discount rate demands; below 1, it destroys value; at exactly 1, it earns the discount rate and nothing more.

Its appeal is that it measures value per dollar committed. Net present value tells you how much wealth a project adds in total, which is the right yardstick for a single yes-or-no decision. When a budget caps what you can spend, though, a project returning $1.50 of present value per dollar may deserve the money ahead of a larger one returning $1.25. That is why the ratio turns up in capital budgeting under spending limits, and in public-sector appraisal under the name benefit-cost ratio.

The same feature misleads when projects are alternatives. Ranked by the index, a $10,000 project with $15,000 of present value (1.5) beats a $100,000 project with $125,000 (1.25), yet the second adds $25,000 of value against $5,000. If only one can go ahead, net present value should decide, which is why the page reports both.

The real work happens before you type anything. The numerator must already be discounted, each year's expected cash flow divided by (1 + r) raised to the number of years, at a rate that reflects the project's risk. Change that rate and the index moves with it; it falls to exactly 1 at the project's internal rate of return.

What is profitability index calculator?

The profitability index, also called the benefit-cost ratio, is the present value of the cash a project is expected to generate divided by the money needed to start it. It has no units. A PI of 1.25 means every dollar invested brings back $1.25 in today's money after allowing for the required return. Some textbooks quote a net version instead, net present value divided by the investment, which is simply the PI minus 1 and would read 0.25 for the same project.

How to use this calculator.

1. 01Discount each future cash inflow to today at your required rate of return and add them up, then enter the total as Present value of future cash inflows. Use after-tax cash flows, not accounting profit.
2. 02Enter the upfront outlay as Initial investment. If the spending is spread over more than one year, enter the present value of those outlays instead.
3. 03Read the index: above 1 accepts the project at your discount rate, below 1 rejects it. The net present value beside it gives the same verdict in dollars.
4. 04When choosing among projects you cannot all afford, run each one and compare both figures, because ranking by index and ranking by net present value can disagree.

The formula.

PI = PV of future inflows ÷ initial investment, and alongside it NPV = PV of future inflows − initial investment. The present value comes from discounting: a cash flow C received in year t is worth C ÷ (1 + r)ᵗ today, where r is the required rate of return. The page takes that sum as an input rather than computing it, so the forecast, the timing and the discount rate are all settled before the division happens. The two outputs always agree on accept or reject, since PI exceeds 1 exactly when NPV is positive. The discount rate usually moves the answer most, because it shrinks distant cash flows far more than near ones. The investment must be at least $0.01, while the present value of inflows may be zero, which gives a PI of 0.

A worked example.

Frequently asked questions.

References& sources.

1. [1]OpenStax, Rice University. Principles of Finance, 2022. Chapters 6–10. Retrieved 2026-08-06.
2. [2]U.S. Internal Revenue Service. Tax guidance current 2026. Official forms, instructions and tax topics. Retrieved 2026-08-06.
3. [3]U.S. Securities and Exchange Commission. Investor.gov current 2026. Investment products and risk. Retrieved 2026-08-06.