The Building Block: How DCF Works
DCF values anything by asking one question: how much are all future cash flows worth in today's money? It is the foundation of modern finance.
FV, r, n) โ or type numbers directly: 10000 / (1 + 0.08)^1010000 / (1 + 0.08)^10Imagine you own a food stall that earns $100 this year, $110 next year, and $121 the year after. What would you sell it for today? DCF tells you exactly that โ by converting every future dollar into today's dollars.
DCF = Sum of all future cash flows, each divided by (1 + rate)^year. The "discount rate" is your required return โ the rate you need to earn to justify the risk. Higher risk โ higher rate โ lower value today.
Imagine you're considering buying a lawn-care business in Texas for $180,000. The owner shows you the books: $35,000 in free cash flow last year, growing about 8% per year for the past three years. Is $180,000 fair? A DCF calculation answers that directly. Discount those future cash flows at a rate that reflects the real risk of owning a small business โ typically 15โ20% โ add a terminal value for what the business would sell for in five years, and sum up the present-day equivalent. If the result is above $180,000, the deal looks attractive. If it's below, you're overpaying.
The same logic applies to a UK property investor looking at a commercial unit in Manchester that generates ยฃ24,000 in net annual rent. At a 7% discount rate, the DCF of that perpetual income stream is simply ยฃ24,000 รท 0.07 = ยฃ342,857. The asking price of ยฃ400,000 implies the rent needs to grow materially to justify the purchase. The calculator lets you model exactly what growth assumption you'd need to make the numbers work โ and whether that growth is realistic.
Warren Buffett famously described the value of any asset as the sum of all future cash flows discounted back to the present. That applies whether you're buying a whole business or 100 shares of a company on the S&P 500. If a company is expected to generate $8 per share in free cash flow next year, growing at 6% annually, a DCF at a 10% discount rate gives a fair value of $8 รท (0.10 โ 0.06) = $200 per share. If it's trading at $150, it may be undervalued. If it's at $250, you're paying a premium the cash flows may not support.
A coffee shop in Austin generates $42,000 in annual free cash flow, growing 5% per year. You require a 16% return for a small-business investment. Over a 5-year explicit forecast, discounting each year's cash flow and adding a terminal value of $42,000 ร (1.05)โต รท (0.16 โ 0.05) โ $616,000 at Year 5: the present value of the Year 1โ5 cash flows is roughly $157,000, and the present value of the terminal value is roughly $296,000, giving a total DCF of about $453,000. If the asking price is $400,000, the deal looks attractive. At $500,000, you're overpaying at a 16% hurdle rate.
A flat in Birmingham generates ยฃ14,400 per year in net rental income after all costs. Assuming a sale in 10 years at ยฃ200,000 and a discount rate of 8%: the present value of 10 years of rent is roughly ยฃ96,600, and the present value of the ยฃ200,000 exit is ยฃ92,640, giving a total DCF of about ยฃ189,240. If the flat costs ยฃ195,000 to buy, the DCF says it is marginally overpriced at an 8% required return. Dropping the discount rate to 7% โ reflecting lower risk or lower alternative returns โ pushes the DCF above ยฃ200,000.
A mid-cap Canadian retailer generates CAD $3.50 per share in free cash flow, growing at 4% annually. At an 11% discount rate (the 4.5% GoC bond yield plus a 6.5% equity risk premium): terminal value per share = $3.50 รท (0.11 โ 0.04) = $50. Discounting the explicit forecast and terminal value back to today gives a fair value of roughly $35โ40 per share. If the stock trades at $30, the model suggests it is significantly undervalued โ assuming the 4% growth and 11% discount rate are well-calibrated.
The discount rate reflects how risky the investment is. For large, stable public companies use 8โ10%. For small private businesses, 15โ25% is more realistic โ they carry far more risk than a blue-chip stock. A useful starting point: use the WACC calculator to find the business's cost of capital, then add a few percentage points if there are significant risks like customer concentration, key-person dependence, or an unpredictable revenue stream.
Terminal value captures all the value beyond your explicit forecast period (usually 5โ10 years). The most common method is the Gordon Growth Model: Final Year CF ร (1 + long-term growth rate) รท (discount rate โ growth rate). Long-term growth should not exceed 2โ3% for a stable business โ roughly the long-run inflation rate. If terminal value exceeds 70% of your total DCF, the answer is very sensitive to that single assumption, so run a sensitivity analysis on it.
A higher DCF means the asset produces more value in present-value terms. But the key comparison is DCF value vs. asking price, not DCF value in isolation. If the DCF is $400,000 and the seller wants $350,000, that's a good deal. If the DCF is $400,000 and they want $500,000, you're overpaying relative to the cash flows. The DCF gives you fair value โ what you pay is a separate negotiation.
A currently unprofitable business can still have a positive DCF if you expect it to become profitable. Model the negative cash flows in the early years and positive ones later โ this is common for startups and growth-phase businesses. The key question is whether the future positive cash flows, discounted back, exceed what you're paying today. The Young Companies calculator on this site handles this specific scenario.
The calculator is mathematically exact โ it applies the DCF formula precisely. The uncertainty lies in your inputs, not the formula. A 2-percentage-point change in discount rate can shift the answer by 30โ40%. A different terminal growth assumption can double the result. Think of DCF as a structured way to make your assumptions explicit and testable, not as a machine that produces one correct answer. Always run at least a base case and a pessimistic case.
Many first-time buyers use 8โ10% for small private businesses because that's what finance textbooks show for large public companies. But a small cafรฉ, retail shop, or service business carries far more risk โ key-person dependence, no diversification, illiquidity, limited track record. Use 15โ25% for small private businesses. A discount rate that's too low inflates the DCF and makes bad deals look attractive.
The 'cash flow' in a DCF is free cash flow โ operating profit after tax, minus net capital expenditure, minus any increase in working capital. If the business earns $60,000 in operating profit but needs $20,000 in new equipment each year and $5,000 more in inventory as it grows, the free cash flow is $35,000 โ not $60,000. Using operating profit overstates value by 70% in that example.
If more than 70โ80% of your DCF comes from terminal value, you are effectively just applying a single-year earnings multiple โ the explicit forecast period is almost irrelevant. That's a valid method, but be honest about it. As a sense check: what exit multiple does your terminal value imply? If it implies selling at 25ร earnings in Year 5, ask yourself honestly whether a buyer would pay that.