NPV / IRR Calculator

• •Use the NPV / IRR Calculator to check your hand calculations on homework or exam problems — comparing its result with your own working helps identify arithmetic errors before they propagate.
• •Use it during the early design phase to rapidly iterate on parameters and narrow down feasible configurations before committing time to detailed finite element simulations or full design packages.
• •Use it when reviewing a colleague's calculation or checking a vendor's data sheet for plausibility — a quick sanity check can prevent costly downstream errors.
• •Use it to generate reference data for a technical report or presentation without manual computation, ensuring consistent, reproducible numbers throughout the document.
• •Use it in the field when a quick estimate is needed and a full engineering software package is not available.

The NPV / IRR Calculator is a precision engineering calculation tool designed for students, engineers, and technical professionals. Enter initial investment and annual cash flows to compute NPV, IRR (bisection), payback period, and discounted payback. NPV vs discount rate chart. All calculations are performed using established engineering formulas from the relevant scientific literature and standards. Follow the units printed beside each field. Where a unit selector is provided, the selected unit is converted internally. Results are computed in your browser without sending data to a server, which keeps your inputs private. This calculator is intended as a supplementary tool for learning and design exploration; always verify results against authoritative references for safety-critical applications.

Net Present Value (NPV) is the sum of all cash flows (inflows and outflows) discounted to present value at a specified discount rate: NPV = Σ [CF_t / (1 + r)^t], where CF_t is the cash flow in period t and r is the discount rate. NPV > 0 means the investment creates value; NPV < 0 means it destroys value; NPV = 0 means it exactly meets the required rate of return. NPV is the standard method for capital investment decisions because it correctly accounts for the time value of money and gives a direct measure of value creation. Internal Rate of Return (IRR) is the discount rate at which NPV = 0: NPV(r = IRR) = 0. IRR represents the 'yield' of an investment — the effective return it earns on money invested. An investment is acceptable if IRR > required rate of return (cost of capital). IRR is computed numerically (bisection or Newton-Raphson) because there's no closed-form solution for general cash flow patterns. Complications: (1) multiple IRRs can exist when cash flows change sign more than once; (2) IRR assumes reinvestment at the IRR rate, which may be unrealistic for high-IRR projects; (3) comparing mutually exclusive projects by IRR alone can give wrong decisions — use NPV or the incremental IRR method. The payback period is the time to recover the initial investment from undiscounted cash flows — simpler but ignores the time value of money.

• •Capital investment decisions: evaluate whether to purchase a new machine, build a new facility, or acquire a company using NPV and IRR analysis.
• •Project prioritization: rank multiple potential projects by NPV (highest NPV first) when capital is constrained.
• •Acquisition valuation: compute the NPV of a target company's projected cash flows to determine maximum reasonable acquisition price.
• •Equipment replacement analysis: compare keeping existing equipment vs buying new using NPV of the incremental cash flows.
• •Public infrastructure evaluation: NPV of benefits minus costs for public projects (roads, bridges, schools), often using social discount rates lower than private.