Why Is a DCF Sensitive to Terminal Value

A DCF explicitly forecasts only 5-10 years of cash flows, but a company generates cash indefinitely, so the terminal value must capture everything after the forecast window — effectively an infinite stream. Because that stream is so much longer than the explicit period, its present value usually swamps the forecasted years, commonly 60-80% of total enterprise value and sometimes more for high-growth firms whose cash flows are back-loaded. The result is that the precision you put into modeling year-by-year revenue and margins matters far less than the two or three assumptions sitting inside the terminal value calculation.

Under the perpetuity growth method, terminal value = final-year FCF × (1+g) / (WACC − g), so a small change in g or WACC has an outsized effect because they appear in a denominator that may already be small (e.g., 9% − 2.5% = 6.5%). A 50 bps move in WACC or g can shift terminal value by 8-15%. Under the exit-multiple method, the multiple chosen (say 8x vs 9x EBITDA) scales terminal value almost linearly, and the multiple is itself a judgment call drawn from comps. WACC additionally compounds: it discounts every cash flow, so raising it lowers both the explicit-period and terminal values simultaneously.

Because no single set of terminal assumptions is defensible as 'the answer,' the standard practice is to present a sensitivity table — a grid showing implied value across a range of WACCs (rows) and perpetuity growth rates or exit multiples (columns). This converts a fragile point estimate into a defensible range. Bankers also cross-check methods: compute terminal value via perpetuity growth and back into the implied exit multiple (and vice versa); if the implied figure is unreasonable, the assumption is recalibrated. A further sanity check is the percentage of total value in terminal — if it's above ~80%, the forecast period may be too short or growth assumptions too aggressive, and the DCF should be treated cautiously.