TL;DR: A DCF calculator values a company as the present value of the free cash flow it will produce: forecast the cash flow for a set number of years, discount each year back at your required return, add a terminal value for everything after the forecast, then subtract net debt and divide by the share count. The worked example below produces $69.81 per share from its stated inputs, and shows that most of that value sits in the terminal value, which is why small changes to the discount rate or growth rate move the answer so much. Treat any DCF output as a statement about your assumptions, not a fact about the stock.
Key Takeaways
- A DCF has five real inputs: starting free cash flow, a growth rate for the forecast years, a discount rate, a terminal growth rate, and the bridge from company value to per-share value (net debt and share count).
- In the worked example, the terminal value contributes about 70 percent of the total value. That proportion is normal, and it is the main reason DCF results are fragile.
- The discount rate is your required return, not a number the calculator knows. Raising it from 10 percent to 12 percent cuts the example's value from $69.81 to $55.12 per share.
- Read the output as a range across sensible inputs, then ask the reverse question with a reverse DCF: what growth does today's price already assume?
- A DCF cannot rescue a company you do not understand. Run the stock research checklist first.
What does a DCF calculator actually calculate?
Discounted cash flow rests on one idea: money arriving later is worth less than money in hand, because money in hand can be invested. So a company is worth the sum of its future free cash flow, with each future year shrunk by a discount factor that reflects how long you wait and what return you require for waiting.
Free cash flow is the cash a business generates after the spending needed to run and maintain it: operating cash flow minus capital expenditure, in the standard definition used in company filings. It is the cash that could, in principle, be returned to owners. A DCF calculator takes that figure as the starting line, grows it for a forecast window, prices the years after the window with a terminal value, discounts everything to today, and hands you a value.
What are the inputs, one by one?
- Starting free cash flow. Last year's figure, or better, a normalized figure across a few years. One unusual year, a big build-out or a one-time windfall, poisons everything downstream.
- Forecast growth rate. Your estimate of how fast free cash flow grows during the explicit forecast window, often five or ten years. This is a research conclusion, not a dial to spin until the answer pleases you.
- Discount rate. The annual return you require for holding this risk. For a whole company this is often framed as the weighted average cost of capital; for your own decision it is your hurdle rate. Higher required return, lower value today. Every time.
- Terminal growth rate. The modest rate at which cash flow is assumed to grow forever after the forecast window. It should sit at or below long-run economic growth. A terminal rate close to the discount rate makes the maths explode, which is the model telling you the assumption is impossible.
- Net debt and shares outstanding. The model values the whole enterprise. Subtract debt, add cash, and divide by the share count to reach a per-share figure you can compare with the price.
A worked example, with the arithmetic shown
The following company is hypothetical and every figure is illustrative. Free cash flow last year was $100 million. Assume it grows at 5 percent a year for five years, your discount rate is 10 percent, and terminal growth after year five is 2 percent.
Forecast free cash flow, in millions: year 1, $105.00; year 2, $110.25; year 3, $115.76; year 4, $121.55; year 5, $127.63.
Discount each year at 10 percent (divide year 1 by 1.10, year 2 by 1.10 squared, and so on): present values are $95.45, $91.12, $86.97, $83.02, and $79.25 million. Together the five forecast years are worth $435.81 million today.
Terminal value at the end of year 5: take year 5 cash flow, grow it once at the terminal rate, and divide by the discount rate minus the terminal rate: $127.63 times 1.02, divided by (0.10 minus 0.02), equals $1,627.26 million. Discounted back five years at 10 percent, that terminal value is worth $1,010.40 million today.
Enterprise value: $435.81 plus $1,010.40 equals $1,446.21 million. Now the bridge: suppose the company carries $50 million more debt than cash, and has 20 million shares outstanding. Equity value is $1,446.21 minus $50, which is $1,396.21 million. Divided by 20 million shares, the DCF value is $69.81 per share.
How should you read that answer?
First, notice where the value lives: $1,010.40 of the $1,446.21 million, about 70 percent, comes from the terminal value, the years you did not explicitly forecast. That is typical of DCF models and it is the honest warning label. The part of the answer built on the vaguest assumption carries most of the weight.
Second, test the fragility before believing anything. Hold everything in the example constant and raise only the discount rate to 12 percent: the value falls to $55.12 per share. Hold the discount rate at 10 percent and set forecast growth to zero instead of 5 percent: the value falls to $56.04 per share. Two plausible assumption changes, each moving the answer by roughly a fifth. A DCF that outputs a single number to two decimal places is performing precision it does not have. Run a small grid of growth and discount combinations and work with the range.
Third, compare against price with a margin of safety mindset, the same discipline behind the Graham Number: a value estimate only helps if the price sits far enough below it to absorb your own errors.
Finally, flip the model around. Instead of asking what your assumptions say the stock is worth, ask what the current price assumes. That is the reverse DCF, and it is often the more honest exercise, because the market's assumption is a fact you can argue with, while your forecast is an opinion you may be fond of.
What a DCF calculator cannot do
It cannot forecast. It cannot tell you whether the growth rate you typed describes the actual business, whether management will allocate capital sensibly, or whether the industry changes shape in year three. It also handles some businesses badly: companies with negative or wildly cyclical free cash flow, and financial companies whose cash flow means something different, produce confident-looking nonsense. The calculator's job is translation, turning beliefs you already hold into a price. The research that should produce those beliefs happens before the calculator opens.
FAQ
What discount rate should I use in a DCF calculator? The return you genuinely require for this level of risk. Many investors use a figure built from the company's cost of capital; others use a personal hurdle rate applied consistently. What matters is that you state it, use it consistently across companies, and check how the answer changes a point or two either side, as the worked example does.
How many years should the forecast cover? Five to ten years is the common range. Shorter windows push even more weight onto the terminal value. Longer windows pretend to knowledge nobody has about a specific company a decade out. The window matters less than knowing which assumption is carrying your answer.
Why is the terminal value so large? Because it stands in for every year after the forecast, forever, compressed into one figure. A business expected to keep producing cash for decades genuinely does hold much of its value in those distant years. The size is not an error. It is a reminder that the terminal growth assumption deserves as much scrutiny as the forecast itself.
What if free cash flow is negative? Then a standard DCF has nothing sound to grip. Investors either model the path to positive cash flow explicitly, year by year, with all the guesswork that involves, or set the tool aside for that company. A calculator that returns a neat value from a negative base without comment is hiding the problem, not solving it.
Sources
- Investor.gov (U.S. Securities and Exchange Commission), investor education material on company filings and financial statements, accessed October 2026.
- U.S. Securities and Exchange Commission, EDGAR company filings database: the source for the cash flow statements any real DCF must start from, accessed October 2026.
Educational content, not financial advice. The worked example uses a hypothetical company and illustrative figures. A DCF output reflects the assumptions entered into it and is not a recommendation to buy or sell any security.
