DCF Explained: How Discounted Cash Flow Works

Short answer: a discounted cash flow (DCF) model estimates what a business is worth today by projecting the cash it will generate in the future and “discounting” those future dollars back to present value. The logic is simple — a dollar you’ll receive in ten years is worth less than a dollar in your hand now — and the output is an estimate of intrinsic value you can compare against the market price.

Why cash flow, not earnings?

You buy a business for the cash it will hand back to owners over its life, not for a headline earnings number. Accounting earnings can be distorted by non-cash charges, one-time items, and timing quirks. Free cash flow — the cash left after the company pays its bills and reinvests to keep running — is closer to what an owner actually receives. That’s why a DCF is built on cash flow.

It’s the same question behind the Margin of Safety pillar — is the price below what the business is worth? (In Market Lens, the margin-of-safety score uses a simpler estimate built from the Graham Number and a fair-P/E value; the DCF is shown alongside it as a separate, cash-flow-based second opinion.)

The three moving parts

A DCF has exactly three inputs that matter. Get these roughly right and the model is useful; get them badly wrong and it’s fiction.

1. Projected cash flows. Your best estimate of free cash flow for the next 5–10 years. This is where the quality of the business matters most — a company with a durable economic moat has more predictable cash flows, which makes the forecast more trustworthy.
2. The discount rate. The annual rate used to shrink future cash back to today’s value. It reflects both the time value of money and the risk that the cash won’t show up. A higher discount rate means you’re demanding more compensation for risk, which lowers the valuation.
3. The terminal value. The value of all the cash flows beyond your explicit forecast window. Because a business can run for decades, a large share of a DCF’s value often sits here.

A full worked example you can follow

Let’s value a small, steady business from scratch. Assume it produces $100 of free cash flow next year, that cash grows 5% a year, and you use a 10% discount rate. We’ll run a five-year forecast, then add a terminal value for everything after year five.

Step 1 — project the cash flows. Start at $100 and grow each year by 5%:

Year	Free cash flow	Discount factor (1.10ⁿ)	Present value
1	$100.00	1.1000	$90.91
2	$105.00	1.2100	$86.78
3	$110.25	1.3310	$82.83
4	$115.76	1.4641	$79.07
5	$121.55	1.6105	$75.47

Add up the present-value column: $415.06. That’s what the first five years of cash are worth in today’s dollars.

Step 2 — add the terminal value. Assume cash grows a slower 2.5% forever after year five. Using the Gordon Growth Model on year-five cash:

Terminal value = ($121.55 × 1.025) / (0.10 − 0.025) = $124.59 / 0.075 = $1,661.20

That $1,661.20 is a year-five figure, so you must discount it back to today — divide by the year-five factor (1.6105): $1,661.20 ÷ 1.6105 = $1,031.48.

Step 3 — add the two pieces. Intrinsic value = $415.06 (explicit years) + $1,031.48 (terminal) = about $1,446.54 for the whole business. Divide by shares outstanding and you have a per-share fair value.

Notice how much of the answer — roughly 71% — sits in the terminal value. That is normal, and it’s exactly why the growth and discount-rate assumptions matter so much: a small change to either swings the terminal piece hard. For a step-by-step definition of the output, see free cash flow and intrinsic value in the glossary.

The terminal value, plainly

The most common method is the Gordon Growth Model, which assumes cash flows grow at a small, steady rate forever (usually near long-run economic growth — a few percent). The formula:

Terminal value = (final-year cash flow × (1 + growth)) / (discount rate − growth)

That’s why the discount rate must always be higher than the perpetual growth rate — otherwise you divide by zero or a negative number and get nonsense. The Market Lens DCF calculator guards against exactly this: if the spread between the two rates isn’t positive, it refuses to produce a fake number rather than print garbage.

The honest truth about DCF: it’s a range, not a number

A DCF’s biggest weakness is also its most important lesson. Small changes to the discount rate or growth assumption swing the answer dramatically. That sensitivity means any single “fair value” number is false precision.

The fix is to run scenarios instead of one guess:

• Bear case — conservative growth, higher discount rate. What is it worth if things disappoint?
• Base case — your realistic expectation.
• Bull case — optimistic but still plausible.

The result is a fair-value band, not a point. Market Lens builds all three automatically: a 10-year projection (5 years of near-term growth, then 5 years fading toward a slower rate), a Gordon Growth terminal value, and a discount rate from the CAPM cost of equity (risk-free rate + the stock’s beta × an equity risk premium) — not a full WACC. The three cases are blended 25% bear / 50% base / 25% bull into one weighted value. The scenario assumptions are fixed by the model; you can’t enter your own inputs. A valuation is an estimate built on assumptions — never a prediction of where the price will go.

Where DCF fits (and where it doesn’t)

A DCF works best for stable, cash-generating businesses whose future is reasonably predictable — the same wide-moat companies that pass the quality test. It works poorly for early-stage companies with no reliable cash flow, deeply cyclical businesses, or anything whose future is a coin flip. For those, other tools like the P/E ratio, price-to-book, and the Graham Number act as sanity checks rather than substitutes.

This is why Market Lens never treats a DCF as the whole answer. It’s one leg of the process — you still start by asking whether it’s a good business and how to find undervalued names in the first place.

How to read a DCF’s sensitivity

The single most useful habit with a DCF is watching how the answer moves when you nudge the two big assumptions. Using the same business above (year-five cash of $121.55), here is roughly how the terminal value alone shifts:

Discount rate	Terminal growth	Terminal value (undiscounted)
9%	2.5%	~$1,917
10%	2.5%	~$1,661
11%	2.5%	~$1,466
10%	1.5%	~$1,452
10%	3.5%	~$1,936

A single percentage point either way moves the number by double digits. That isn’t a flaw you can engineer away — it’s the honest nature of valuing far-off cash. The takeaway: treat a DCF as a band of plausible values, and never present one decimal-perfect figure as the truth.

Common mistakes with a DCF

• Treating the output as a prediction. A DCF estimates value under a chosen set of assumptions. It is not a forecast of where the share price will go — and nothing here tells you to buy or sell.
• Over-trusting the terminal value. Most of the answer usually lives in the terminal value. If your perpetual growth rate is even slightly too high, the whole model inflates. Keep it at or below long-run economic growth (a few percent).
• Setting the discount rate below the growth rate. If the discount rate isn’t higher than the perpetual growth rate, the Gordon Growth formula divides by zero or a negative number and prints nonsense. The Market Lens DCF calculator refuses to produce a number in that case rather than fake one.
• Running a DCF on the wrong kind of company. Early-stage, deeply cyclical, or unpredictable businesses have no reliable cash flow to project, so a DCF there is a guess dressed up as math.
• Using one scenario instead of three. A single point estimate hides the risk. Bear/base/bull forces you to see the range.

Frequently asked questions

What is a discounted cash flow model in simple terms?

A DCF estimates what a business is worth today by projecting the cash it will produce in future years and shrinking each future dollar back to its present value, because a dollar years from now is worth less than a dollar today. Add up all those present values — including a terminal value for the years beyond your forecast — and you get an estimate of intrinsic value.

Why is the discount rate so important?

Because it sets how harshly future cash is penalized for time and risk. A higher discount rate lowers the valuation; a lower one raises it. As the sensitivity table shows, a single percentage point can move the answer by double-digit percentages, which is why Market Lens uses a transparent, fixed-default rate (a CAPM cost of equity) rather than a number tuned to flatter any one stock.

What is a terminal value?

The terminal value captures all the cash flows beyond your explicit forecast window — often the majority of a DCF’s total. Market Lens uses the Gordon Growth Model (cash growing at a small, steady rate forever) and then discounts that figure back to today, just like every other year.

Is a DCF better than the P/E ratio?

Neither is “better” — they answer different questions and work best together. A DCF is a cash-flow-based estimate of value; the P/E ratio is a quick market-expectation gauge. Market Lens shows the DCF as a separate second opinion alongside the P/E and the Graham Number, so you can cross-check one tool against another.

Putting it together

A DCF is just disciplined common sense: a business is worth the cash it will produce, and future cash is worth less than cash today. Estimate the cash, discount it, add a terminal value, and demand a range instead of a false-precision number. Then compare that range to the price and insist on a cushion.

You can read the exact formulas on the methodology page, run a full quality-plus-valuation workup in the Stock Analyzer, or see the bear/base/bull scenarios for any stock in the DCF calculator.

Market Lens is educational research, not investment advice. Every figure is an estimate from public data that may be delayed or incomplete.