What is NPV & IRR Calculator?
Net present value (NPV) and internal rate of return (IRR) are the two workhorses of investment appraisal. NPV answers “how much value does this project add in today's money?” by discounting every future cash flow back to the present and subtracting the initial outlay. IRR answers the mirror question: “what yearly return does this stream generate?” — it is the discount rate at which NPV falls to exactly zero.
This calculator computes NPV, IRR, MIRR, the profitability index, and both simple and discounted payback from any cash-flow stream, with a period-by-period discounting schedule. It can compare two projects head-to-head (including the crossover rate), run a sensitivity grid over discount rates and cash-flow multipliers, solve for the rate or outlay that hits your target, and chart the NPV profile so you can see exactly where the decision flips.
When to Use This Calculator
- Ranking capital projects when a budget forces you to choose between investments.
- Deciding whether a startup, product, or campaign budget clears your cost of capital.
- Comparing two mutually exclusive projects with different cash-flow timing.
- Evaluating solar panels, equipment, or efficiency upgrades against decades of savings.
- Screening an R&D or expansion pipeline for projects that only look good on IRR.
- Any decision where money arrives in different years and you must pick one option.
Steps:
- List every cash flow by period — the initial outlay goes at time 0 (as a negative flow), and each period's net cash receipt goes on its own row.
- Choose the cash-flow frequency — annual, quarterly, or monthly. The discount rate you enter must be for one period of that frequency.
- Enter your discount rate — usually the project's weighted average cost of capital or the return your next-best alternative offers.
- Read the NPV and verdict — a positive NPV means the project earns more than the discount rate; a negative one means it destroys value at that rate.
- Check IRR against the hurdle rate — IRR above the hurdle means the project clears your cost of capital; MIRR shows what happens when reinvestment is more realistic.
- Stress-test the answer — use the sensitivity grid to see how NPV behaves if cash flows come in 30% lower or the required rate climbs, before committing real money.
Formula
Net present value:
NPV = sum(t=0..n) CF_t / (1 + r)^t
Internal rate of return (IRR):
the rate r such that NPV(r) = 0
Modified IRR:
MIRR = ( FV(positive flows at reinvest rate)
/ -PV(negative flows at finance rate) )^(1/n) - 1
Profitability index:
PI = PV(cash inflows) / initial outlay
Discount factor for period t:
DF_t = 1 / (1 + r)^t
Annual to periodic rate:
r_period = (1 + r_annual)^(1/n) - 1
Where:
CF_t = net cash flow at period t (t = 0 is the initial outlay)
r = discount rate per period
n = number of periods
Accept when NPV > 0, or when PI > 1.
Use Cases
- Capital budgeting — ranking machines, vehicles, and equipment projects by NPV per dollar invested (PI) when the budget is limited.
- Startup and product investment — testing whether a venture's projected cash flows justify the runway it consumes at a venture-grade hurdle rate.
- Marketing spend evaluation — comparing a campaign's incremental cash flows against the company's cost of capital before renewing the budget.
- Solar and efficiency upgrades — verifying that decades of energy savings beat the upfront cost at your actual electricity discount rate.
- R&D portfolio screening — killing projects whose IRR looks positive but sits below the firm's hurdle rate.
- Personal finance decisions — rent-vs-buy, education costs, or any trade-off where money arrives in different years.
Key Benefits
- Three modes in one tool — NPV, IRR & MIRR, and a head-to-head project comparison with the crossover rate.
- Full pro stack — sensitivity grid, scenario snapshots, goal solver, animated discounting diagram, and three live charts.
- Period-aware inputs — annual, quarterly, or monthly cash flows with a built-in annual-to-periodic rate converter.
- Every metric, verified — NPV, IRR, MIRR, PI, simple and discounted payback computed from the same stream, with number-perfect worked examples.
- Free and instant — no sign-up, shareable URL state, CSV export and print report, works on phone, tablet, and desktop.
Pro Tips
- Quick rule: accept when NPV > 0 and PI > 1; when capital is rationed, rank by PI and take the highest first.
- If NPV and IRR disagree, trust NPV — the disagreement always traces back to an implicit reinvestment assumption that MIRR makes explicit.
- The crossover rate is the discount rate where both projects' NPVs are equal; below it one project wins, above it the other does.
- Use the sensitivity grid before committing: if the decision flips when cash flows dip only 10%, the project has no margin for error.
- Discounted payback is always later than simple payback — the gap is the cost of waiting for your money.
Common Mistakes to Avoid
- Discounting at an annual rate while entering monthly cash flows — match the rate to the frequency, or convert it with the built-in periodic-rate converter.
- Accepting on IRR alone — a 20% IRR on a tiny project adds less wealth than a 12% IRR on a huge one; NPV (and PI when capital is rationed) measures size, IRR only measures rate.
- Treating a positive IRR as automatically good — an IRR of 2.46% is positive, but if your hurdle is 15% the project still destroys value relative to the alternative.
- Double-counting the outlay — the initial investment belongs at time 0 as a negative flow; do not subtract it again from the NPV the calculator reports.
- Believing payback is a profitability measure — payback ignores everything after the cutoff and the time value of money inside the window; use it only as a liquidity screen.
Key Terms Explained
- Net present value (NPV):
- The sum of all cash flows discounted to today, NPV = Σ CFₜ/(1+r)ᵗ. Positive NPV means the project earns more than the discount rate.
- Internal rate of return (IRR):
- The discount rate that makes NPV exactly zero — the average annual return the stream generates.
- Modified IRR (MIRR):
- A reinvestment-corrected return: future positives compound at your reinvestment rate, upfront negatives are financed at your finance rate.
- Profitability index (PI):
- PV of inflows divided by the initial outlay — the present value created per dollar invested (PI > 1 accepts).
- Discount rate:
- The required return per period used to convert future money into present money; often the firm's WACC or an opportunity cost.
- Crossover rate:
- The discount rate at which two competing projects have the same NPV — the point where the preferred choice switches.
Related Concepts
- Weighted Average Cost of Capital (WACC): The blended funding cost most often used as the discount rate — the hurdle every accepted project must clear.
- Discounted Cash Flow (DCF): The valuation family this calculator belongs to: price any asset as the present value of its future cash flows.
- Payback Period: The liquidity screen that ignores interest — shown here both plainly and in its discounted, time-value-aware form.
- Capital Rationing: The constraint that makes profitability index the ranking tool when the budget cannot fund every positive-NPV project.
- NPV Profile: The chart of NPV against the discount rate — its slope shows sensitivity and its x-intercept is the IRR.
Example
Equipment purchase. A machine costs $10,000 today and returns $3,000, $4,000, $5,000 and $4,000 over four years. Your discount rate is 8%.
Discount each year: 3,000/1.08 + 4,000/1.08² + 5,000/1.08³ + 4,000/1.08⁴ = 2,777.78 + 3,429.36 + 3,969.16 + 2,940.12 = $13,116.41
NPV = 13,116.41 − 10,000 = $3,116.41 — accept, the project adds value.
The IRR is 20.50%, well above the 8% hurdle, and the profitability index is 13,116.41/10,000 = 1.31 — every $1 invested returns $1.31 in present value. Simple payback lands at 2.60 years; discounted payback, the stricter test, at 2.96 years.
Interpreting Your Results
Start with the NPV sign: positive NPV means the stream earns more than the discount rate and adds wealth; negative NPV means it falls short. Next compare IRR with the hurdle rate — IRR above the hurdle means the project clears your cost of capital, while an IRR below it fails even if NPV terms look tempting at a lower rate. Then read PI: above 1.0 every dollar invested brings back more than a dollar in present value; 1.31 is strong, 0.66 means you lose 34 cents of value per dollar. Finally watch the payback pair: simple payback ignores the time value of money, so discounted payback is always later — the gap between them is the cost of waiting for your money. When NPV and IRR disagree, trust NPV and let MIRR explain the reinvestment assumption behind the difference.