What is the NPV formula and how does this tool apply it?

Net present value discounts every future cash flow back to today and subtracts the initial outlay: NPV = the sum over each period t of CFt divided by (1 + r) to the power t. The period-0 flow divides by (1 + r) to the 0, which equals 1, so the money you spend today counts at face value. Example: at a 10% rate, [-1000, 500, 500, 500] gives 500/1.1 + 500/1.21 + 500/1.331 minus 1000, which is about 243.43. A positive result means the inflows, in today's money, beat the outlay.

What does the discount rate actually do?

The discount rate is the return you could earn elsewhere on money of the same risk, so it is the price of waiting. A dollar a year out is worth less than a dollar today because today's dollar could be invested. Raising the rate shrinks every future cash flow's present value, so NPV falls as the rate rises. At 5% the same [-1000, 400, 400, 400, 400] series is clearly positive; push the rate to 25% and it can turn negative, because distant inflows get discounted hard.

Why does NPV greater than zero mean the project is worth doing?

A positive NPV says the project's inflows, valued in today's money, more than cover the cash you put in, after charging your discount rate as the cost of capital. So it adds value beyond what you would earn just leaving the money in your benchmark alternative. NPV exactly zero means it breaks even at that rate, and negative means a comparable lower-risk investment would do better. Among competing projects, the higher NPV usually wins, assuming similar scale and risk.

What is IRR and how is it different from NPV?

The internal rate of return is the single discount rate that makes NPV exactly zero. For [-1000, 500, 500, 500] the IRR is about 23.36%, meaning the project effectively earns 23.36% a year on the money tied up in it. You compare IRR against your required rate: if IRR beats the hurdle, NPV at that hurdle is positive. NPV is in currency, IRR is a percentage; IRR can mislead on projects of different sizes or with flows that flip sign more than once, so finance teams lean on NPV as the tiebreaker.

How should I sign the cash flows?

Money leaving you is negative, money coming in is positive. The initial investment is almost always a negative period-0 entry. Later periods are usually positive inflows, but a year with extra capital spending or a tax bill can be negative too, and the tool handles a mix. Getting signs right matters: flip the initial outlay to positive by accident and NPV balloons into nonsense. The IRR solver also needs at least one sign change in the series, which a correctly signed outlay-then-inflows pattern provides.

What does the payback period tell me that NPV does not?

Payback is how long until cumulative cash flow turns positive and you have recovered the initial outlay. For -1000 followed by 500 a year, payback is 2.0 periods; -1000 then 400 a year recovers at 2.5, interpolated within the year. It is a quick liquidity and risk gauge, shorter is safer, but it ignores the time value of money and anything that happens after recovery. Use it alongside NPV, not instead of it: a project can pay back fast yet still have a low NPV, or pay back slowly yet create far more value over its full life.

Decide whether a capital project is worth the money

You are weighing a 1,000,000 machine that should throw off about 300,000 a year for five years. Enter the outlay as a negative period-0 flow, list the five annual inflows, and set your cost of capital as the discount rate. The NPV tells you, in today's money, whether the inflows beat the spend after charging that rate. A positive number is a green light; a negative one says the same money parked in your benchmark would do better.

Rank two projects competing for one budget

Two proposals both need roughly the same upfront cash, but their cash flows arrive on different schedules. Run each through the calculator at the same discount rate and compare NPVs head to head. The higher NPV wins because it adds more value in today's terms. Read the IRR alongside to sanity-check, and watch for the classic trap where a smaller project shows a flashier IRR but a smaller NPV.

Value an income stream you are thinking of buying

A rental, a royalty, or a small business is really just a series of future cash flows. Estimate each year's net cash, set a discount rate that reflects the risk, and the present-value-by-period table shows how much each year contributes to the price you should pay. If the asking price is below the NPV of the inflows, the deal is creating value for you at that rate.

Check homework or model a DCF for a finance class

Time-value-of-money problems are easy to get wrong by one period or one sign. Paste the textbook cash flows, set the rate, and verify the NPV and IRR against the answer key, then read the per-period present values to see exactly which term you fumbled. The shareable URL lets you send the worked example to a study partner who opens it with your numbers already in.

NPV Calculator — Net Present Value, IRR and Payback

Discount every cash flow back to today — net present value, IRR, payback period, per-period present value — browser-only

Runs locally
Category Calculator
Best for Getting a realistic range before a purchase, plan, workout, or schedule decision.

Cash flow inputs

Initial investment (period 0)

Money spent today. Enter it as a negative number.

Discount rate (% per period)

Cash flows (one per line, period 1, 2, 3 …)

One amount per line. Inflows positive, outflows negative.

Result

Net present value

243.43

Internal rate of return (IRR)

23.38%

Payback period

2.00 periods

NPV is positive, so the project clears your discount rate.

Present value by period

Period	Cash flow	Discount factor	Present value
0	-1,000	1.0000	-1,000
1	500	0.9091	454.55
2	500	0.8264	413.22
3	500	0.7513	375.66

What this tool does

A net present value calculator for capital budgeting, project appraisal and finance coursework. Enter the initial investment as a period-0 cash flow (negative, since it is money spent today), list each later period's cash flow one per line, set a discount rate, and the tool discounts every future amount back to today with NPV = sum of CFt over (1 + r) to the t, minus the outlay you already counted at face value. You get the headline net present value, the present value of each individual period so you can see where the money actually comes from, and a feasibility read: a positive NPV means the project clears the rate you set, a negative one means it does not. It also solves for the internal rate of return, the discount rate that drives NPV to zero, using Newton iteration with a bisection fallback so awkward series still converge, and reports the simple payback period with fractional interpolation. The discount rate and the full cash-flow list ride in a shareable URL, and every figure is computed in your browser with no server call.

Tool details

Input: Text + Numbers; The page exposes text boxes, numeric controls, file pickers, or structured inputs depending on the tool.
Output: Live result + Copy; The result area focuses on usable output, with copy, download, or preview actions when supported.
Privacy: Browser-side processing; The main tool logic does not call an external API, so inputs normally stay in the current tab.
Save / share: Shareable URL state; Key settings are encoded in the URL so another person can reopen the same setup.
Performance budget: Initial JS <= 10 KB; No WASM budget is declared, keeping the tool quick to open on mobile.
Best fit: Calculator · Finance; Category and role tags drive related tools, internal links, and quick fit checks.

How to use

1. Input

Paste or drop your content into the tool panel.
2. Process

Click the button. All processing is local in your browser.
3. Copy / Download

Copy the result or download to disk in one click.

How NPV Calculator fits into your work

Use it for fast estimates, comparisons, and planning numbers before you make the final call.

Calculation jobs

Getting a realistic range before a purchase, plan, workout, or schedule decision.
Comparing scenarios by changing one input at a time.
Turning rough assumptions into a number you can discuss.

Calculation checks

Double-check units, dates, rates, and rounding assumptions.
Treat health, finance, tax, and legal outputs as planning aids, not professional advice.
Save the inputs that produced an important result so you can reproduce it later.

Good next steps

These links move the current task into a more complete workflow.

Real-world use cases

Decide whether a capital project is worth the money
You are weighing a 1,000,000 machine that should throw off about 300,000 a year for five years. Enter the outlay as a negative period-0 flow, list the five annual inflows, and set your cost of capital as the discount rate. The NPV tells you, in today's money, whether the inflows beat the spend after charging that rate. A positive number is a green light; a negative one says the same money parked in your benchmark would do better.
Rank two projects competing for one budget
Two proposals both need roughly the same upfront cash, but their cash flows arrive on different schedules. Run each through the calculator at the same discount rate and compare NPVs head to head. The higher NPV wins because it adds more value in today's terms. Read the IRR alongside to sanity-check, and watch for the classic trap where a smaller project shows a flashier IRR but a smaller NPV.
Value an income stream you are thinking of buying
A rental, a royalty, or a small business is really just a series of future cash flows. Estimate each year's net cash, set a discount rate that reflects the risk, and the present-value-by-period table shows how much each year contributes to the price you should pay. If the asking price is below the NPV of the inflows, the deal is creating value for you at that rate.
Check homework or model a DCF for a finance class
Time-value-of-money problems are easy to get wrong by one period or one sign. Paste the textbook cash flows, set the rate, and verify the NPV and IRR against the answer key, then read the per-period present values to see exactly which term you fumbled. The shareable URL lets you send the worked example to a study partner who opens it with your numbers already in.

Common pitfalls

Signing the initial investment positive. The period-0 outlay is money leaving you, so it must be negative. Enter +1000 instead of -1000 and the NPV inflates by 2000 and the whole feasibility read flips. The tool labels period 0 as the initial investment and hints to make it negative, but it cannot guess your intent.
Confusing the per-period rate with an annual rate when periods are not years. The discount rate must match the cash-flow period. If your flows are quarterly, a 12% annual rate is roughly 3% per quarter, not 12% per quarter. Feeding the annual figure to quarterly flows under-discounts everything and overstates NPV.
Treating IRR as a substitute for NPV. IRR is a rate, not value, and it breaks down when projects differ in size or when cash flows change sign more than once, which can produce multiple IRRs. Pick the project with the higher NPV at your true cost of capital, and use IRR only as a cross-check.

Privacy

Every step here, discounting each cash flow, summing the NPV, the Newton and bisection iterations for IRR, and the payback walk, is plain JavaScript running in your browser tab. No investment figure, cash-flow list or rate ever leaves the page, and nothing is logged. The one caveat: the shareable URL encodes your discount rate and cash flows in the query string, so a share link pasted into chat will record those numbers in the recipient server's access log. For a confidential deal model, use the copy button and paste the text rather than sharing the URL.

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NPV Calculator — Net Present Value, IRR and Payback

What this tool does

Tool details

How to use

1. Input

2. Process

3. Copy / Download

How NPV Calculator fits into your work

Calculation jobs

Calculation checks

Good next steps

Real-world use cases

Decide whether a capital project is worth the money

Rank two projects competing for one budget

Value an income stream you are thinking of buying

Check homework or model a DCF for a finance class

Common pitfalls

Privacy

FAQ

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