NPV Calculator
Present value analysis.
Calculate the Net Present Value of a series of cash flows for an investment decision, given discount rate and project length.
What this tool does
Net Present Value discounts future cash flows at a chosen rate and subtracts the initial investment. This calculator takes your initial investment, annual cash flow, project length in years, and discount rate to return the NPV figure. A positive result indicates the project adds value when measured against your discount rate; a negative result suggests it destroys value at that rate. The discount rate and project duration drive the result most significantly—higher rates reduce future cash flows' present value, while longer timelines allow more cash inflows to accumulate. This tool models a simplified scenario with constant annual cash flows and doesn't account for timing variations, inflation adjustments, or tax impacts. The output is for educational illustration of how cash flow timing affects investment comparison.
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Formula Used
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Disclaimer
Results are estimates for educational purposes only. They do not constitute financial advice. Consult a qualified professional before making financial decisions.
Net Present Value (NPV) discounts future cash flows back to today's value, then subtracts initial investment. NPV positive = accept, NPV negative = reject. Formula: NPV = Σ(CF_t / (1+r)^t) - Initial Investment. The discount rate r reflects opportunity cost of capital plus risk premium.
Example: 100,000 invested, 25,000 annual cash flow for 5 years, 8% discount rate. PV of cash flows = 99,818. NPV = 99,818 - 100,000 = -182. Marginal reject - barely fails to clear hurdle. Same project at 7% discount: NPV = 2,565 (accept). Discount rate selection critically affects decision.
NPV vs IRR: NPV gives absolute value (£), IRR gives rate (%). Both important. Profitability Index (PI) = PV of cash flows / initial investment - useful for ranking projects when capital constrained. PI > 1 = positive NPV. Choose highest PI projects when can't fund all positive NPV projects. WACC commonly used as discount rate for corporate projects (typically 7-12%).
Quick example
With initial investment of 100,000 and annual cash flow of 25,000 (plus years of 5 years and discount rate of 8%), the result is -182.25. Change any figure and watch the output shift — it's often more useful to see the pattern than to memorise the formula.
Which inputs matter most
You enter Initial Investment, Annual Cash Flow, Years, and Discount Rate %. Not every input has equal weight. Adjusting one input at a time toward extreme values shows which ones move the result most.
What's happening under the hood
NPV = sum of (cash flow_t / (1 + discount rate)^t) for all years, minus initial investment. The formula is listed in full below. If the number looks off, you can retrace the calculation by hand — that's the point of showing the working.
Where this fits in planning
This is a "what-if" tool, not a forecast. Use it to test ideas before committing: what happens if the rate is 2% lower than hoped, what happens if you add five more years. The value is in the scenarios you run, not the single answer you get from the defaults.
What this doesn't capture
Steady-rate math ignores real-world volatility. Actual returns are lumpy; sequence-of-returns risk matters most in drawdown; fees and taxes drag on compound growth; and behaviour changes in drawdowns can reduce outcomes below the projection. The number represents one scenario rather than a forecast.
££100,000 initial, ££25,000×5y at 8% = -182.25.
Inputs
This example uses typical values for illustration. Adjust the inputs above to match a specific situation and see how the result changes.
Sources & Methodology
Methodology
The calculator computes net present value by discounting each year's cash flow back to today's value using the supplied discount rate, then summing all discounted flows and subtracting the initial investment outlay. Specifically, it divides each annual cash flow by (1 plus the discount rate) raised to the power of that year, accumulates these present values across the full time horizon, and deducts the upfront capital required. The model assumes a constant discount rate throughout the period and treats cash flows as occurring at uniform intervals. It does not account for taxes, fees, inflation adjustments beyond the discount rate itself, or variations in cash flows across years—all inputs are modelled as fixed or linear. The result reflects a point-in-time calculation and is sensitive to the discount rate assumption.
References
Frequently Asked Questions
NPV decision rule?
How to choose discount rate?
NPV vs IRR ranking?
Profitability Index (PI)?
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