The DCF Formula: Putting It Together

If you’ve been following along, you now know that cash is king and that stock prices are driven by expectations. You’ve looked at the income statement to see how much money they make, and you’ve looked at the balance sheet to see how strong they are.

But there is a missing piece of the puzzle: How do we turn all that information into a specific dollar value?

You cannot just look at a stock price and say, "Is it expensive or cheap?" without a standard. We need a yardstick. We need to know what the business is worth to us, today, based on the cash it will generate in the future.

This is where the Discounted Cash Flow (DCF) model comes in. It is the most famous—and most misunderstood—method in investing. It is not a crystal ball, but it is a powerful way to organise your thoughts about value.

The Core Idea: The Time Travel Machine

To understand DCF, you have to understand one fundamental concept: Money in the future is worth less than money today.

Given £100 today you can invest it and earn a return. Given £100 in five years you cannot do anything with it for five years — and it may never arrive at all.

The discount rate — as defined in the previous lesson, the annual return you require to accept the wait and the risk — is what converts a future amount into a present one.

(A note on terminology, because sources vary. Discounting cash flows available to shareholders uses the cost of equity. Discounting cash flows available to the whole firm, before debt is serviced, uses WACC, which blends the cost of equity with the after-tax cost of debt. This lesson values the whole firm and then subtracts debt, so WACC is the appropriate rate here. They are not interchangeable, and using one where the other belongs biases the answer systematically.)

The DCF Formula answers one question:"If I assume a reasonable return for my money (the Discount Rate), what is the maximum amount I should pay for this company today based on what it will earn in the future?"

The Inputs: What You Need to Know

Before you start, gather the raw materials. The DCF calculator will run the arithmetic once you have them. The DCF is only as good as your inputs. You are not calculating magic numbers from thin air; you are translating reality into value.

Here is what you need:

1. Free cash flow forecasts. Operating cash flow minus capital expenditure, projected across the forecast period. This is the cash genuinely available to the providers of capital. See the previous lesson for building these.
2. A discount rate. Built from the gilt yield, an equity risk premium and a company-specific adjustment — typically 8–12% for an established company. Higher risk means a higher rate, which means a lower present value.
3. Net debt and share count. Both from the latest balance sheet. Needed for the final step, which converts a business valuation into a per-share figure.

The Mechanics: How It Works

Once you have your Cash Flow projections and your Discount Rate, the math is actually quite simple, even though the result looks impressive.

The Formula

Present value of year t = FCFₜ ÷ (1 + r)^t

where r is the discount rate and t is the number of years away. Every future amount gets divided by (1 + r) raised to its year number. That is the entire mechanic.

A Complete Worked Example

A company with a discount rate of 9%, forecast over five years, then a terminal value. Every row uses the same rate — this matters, and is the second most common place beginner models go wrong.

Steps 1 and 2 — project, then discount each year:

Note how the present values barely rise even though the cash flows grow 34% across the period — discounting is eating almost exactly as fast as the business is growing. That is what a 9% rate does.

Step 3 — the terminal value. Assume 2.5% perpetual growth after year 5:

TV = £134m × 1.025 ÷ (0.09 − 0.025) = £137.4m ÷ 0.065 = £2,113m

Step 4 — discount the terminal value back. This is the step people skip. That £2,113m sits at the end of year 5, so it is discounted exactly like the year 5 cash flow:

£2,113m ÷ 1.09⁵ = £2,113m ÷ 1.539 = £1,373m

Step 5 — sum to enterprise value:

Note that terminal value is 75% of the total. Three-quarters of this valuation rests on one assumption about the years after the forecast ends.

Step 6 — From Enterprise Value to a Share Price

Enterprise value is the value of the whole business. Shareholders come after lenders, so two more steps are needed — and this bridge is routinely omitted in beginner models, which then compare an enterprise value against a share price and reach a badly wrong conclusion.

Divide by shares in issue — say 500m:

£1,518m ÷ 500m = £3.04, or 304p per share

Now you have something comparable to a share price. If the shares trade at 210p, your assumptions imply they are worth meaningfully more. If they trade at 295p, the model has told you nothing — that gap is well inside your own margin of error.

Intrinsic Value vs. Market Price

This is the most critical comparison in investing.

• Market Price: What the crowd is actually paying. It is influenced by fear, greed, hype, and daily news.
• Intrinsic Value: What the business is actually worth based on its cash generation. It is grounded in reality.

When the market price is above your estimate, your assumptions imply the shares cost more than the business is worth to you.

When it is below, your assumptions imply the opposite.

Two qualifications worth holding onto. First, "the market must eventually agree with me" is an assumption, not a law — markets can disagree with a well-built model for years, and sometimes the market is right and the model is wrong. Second, your estimate carries a wide error band, so only a large gap is informative.

Sum of Parts: Breaking the Puzzle

Some companies are confusing. They might own a profitable factory, a risky tech division, and some cash. A single DCF for the whole company might be messy.

This is where the Sum of Parts (SOP) analysis comes in.

It is like breaking a pizza into slices.

1. You value the "Cash Division" by looking at how much interest it earns.
2. You value the "Profitable Factory" by estimating its cash flows.
3. You value the "Risky Tech Startup" separately (using a higher discount rate because it's risky).

The Rule: If you add up the value of all the parts, you often get a clearer picture than looking at the whole company. It can also help you spot hidden value—like a piece of the company that is being ignored by the market.

Why DCF Can Be Deceptive

Don't be fooled into thinking that because the DCF uses numbers, it is perfect.

1. The Input Trap: Garbage in, garbage out. If your Cash Flow projections are unrealistic (e.g., assuming 50% growth for 10 years), your DCF will be trash. If your Discount Rate is guesswork, the whole calculation shifts.
2. The "Irrationality" Factor: DCF assumes people are rational. It assumes that over time, the stock price will gravitate toward the true value. But in the short term, the market can be completely irrational. A business you value at 300p can trade at 600p for years. Being early and being wrong are indistinguishable at the time, and both feel identical while you wait.
3. False precision. A model producing "304p" invites more confidence than the inputs support. Round your conclusions to reflect what you actually know — "somewhere around 300p, with a wide band" is more honest and more useful.

The Mental Model to Remember

When you use DCF, keep this thought in your head:

"I am not predicting the future. I am working out what I would have to believe to justify today's price."

To be clear, because this is sometimes stated far too optimistically: you do not win either way. If the company performs worse than your forecast, you lose money — a DCF offers no protection against being wrong.

What a wide gap between your estimate and the market price gives you is room to be wrong and still do acceptably. If you value a company at 400p and pay 250p, the business can underperform your forecast meaningfully and you may still be all right. Pay 390p and you need to be close to correct. That is the whole idea of a margin of safety, and it is the subject of the next lesson.

Summary

• DCF Measures Intrinsic Value: It calculates what a business is worth today based on its future cash flows.
• Time Travel: It uses a Discount Rate to move future money back to the present.
• The Calculation: Add up the Present Value of future cash flows plus a Terminal Value.
• Intrinsic vs market: compare the two, but only act on a gap wide enough to survive your own estimation error. A narrow gap is noise.
• Sum of Parts: Break a complex company down into individual cash-generating units to value it more accurately.
• Reality Check: The math is only as good as your assumptions. DCF helps you be rational, but don't be surprised if the market disagrees for a long time.

Disclaimer: This lesson is for educational purposes only and does not constitute financial advice. Discounted Cash Flow models are complex and rely heavily on estimates. Always do your own research.