The Profitability Index (PI) measures how much value an investment generates for every dollar invested, helping compare project profitability.
Compute Profitability Index (PI) from an initial investment, a discount rate, and either fixed or varying cash flows by year.
Meaning:
Example:
A project costs $10,000 and generates $3,000 per year for 5 years, with a 10% discount rate.
Step 1: Calculate PV of inflows
Step 2: Apply the PI formula
Result:
Since PI > 1, the project is profitable and should be accepted.
The total amount you plan to invest (e.g., 10,000).
Choose Fixed Each Year if yearly cash inflows are the same, or Varying by Year if they differ.
The annual required rate of return (e.g., 10%).
How long the project will generate cash flows (e.g., 5).
The expected annual inflow (e.g., 3,000).
- NPV: PV of inflows − initial investment
- Decision: Accept if PI > 1, Reject if PI < 1
Example:
For a $10,000 investment, 10% discount rate, 5 years, and $3,000 cash flow per year → PI = 1.137, Decision: Accept.
Use it when you need to decide whether to go ahead with a project and especially when you’re comparing multiple investment options under a limited budget. It gives you a clear ratio of value created per dollar invested.
If the project has massive up-front investment but low relative returns, or if cash-flows are highly uncertain, the PI may look acceptable (>1) but still mask risk or poor absolute yield. Also, PI doesn’t account for project size fully — a small high-PI project might generate less value than a large lower-PI one.
Yes—though originally a corporate tool, you can apply it to any investment requiring an initial outlay and future returns. Just ensure you discount future cash-flows properly (adjusting for risk/time) and compare to what the initial investment is.
They affect it drastically. If you set an overly optimistic discount rate (too low) or over-estimate future cash invites, you’ll overstate the PI. Conversely, pessimistic estimates reduce PI. It’s only as accurate as those inputs, so you should stress-test assumptions before relying on the PI.
If PI > 1 → the project creates value and is generally acceptable. If PI = 1 → it breaks even, so only pursue if strategic reasons justify it. If PI < 1 → value is destroyed, likely reject. After that, compare to other metrics (like NPV or IRR) and consider project constraints, risk, and size to make the final call