Data & spreadsheets · DCF Calculator
Nominal or Real Cash Flows: Matching Inflation to Your DCF Discount Rate
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Mixing inflation-adjusted cash flows with a nominal discount rate is one of the quietest ways to get a DCF wrong. This post explains the consistency rule, the Fisher relationship and how to audit your own inputs.
A model that looks right and is off by the inflation rate every year — how mismatched cash flows and rates compound into a large error
A DCF can be internally tidy and still be inconsistent. Forecasting purchasing-power cash flows while discounting them with a rate that includes inflation applies the inflation penalty without including the corresponding cash-flow growth. Because that mismatch repeats at every exponent, the gap widens through the forecast instead of appearing as one obvious broken cell.
Nominal versus real: two ways to state one cash flow — what each means and why a forecast must pick one basis and keep it
A real cash flow is stated in constant purchasing-power units; a nominal cash flow includes the assumed change in prices. Neither basis is inherently better. The discipline is to choose one and keep revenue, costs, reinvestment, terminal growth and the discount rate on that same basis, so numerator and denominator describe the same economic units.
The Fisher relationship — how a nominal rate, a real rate and expected inflation tie together, and why simple subtraction is only an approximation
The exact conversion is one plus the nominal rate equals one plus the real rate multiplied by one plus expected inflation. Simple subtraction drops the product term, so it is only an approximation. If a hypothetical real rate is 5% and inflation is 2%, the matching nominal rate is 7.1%, not exactly 7%.
Which basis your discount rate is on — why market-derived rates such as WACC are nominal by default and what that implies for the cash flows
A WACC assembled from observed borrowing costs and required equity returns is normally expressed in nominal terms when those component rates include inflation expectations. The repository does not label a rate as nominal or real and supplies no market inputs, so the modeller must determine the basis before entering it rather than expecting the calculator to infer intent from a percentage.
Growth rates need the same treatment — why a terminal growth assumption must share the basis of the discount rate
Terminal growth belongs to the same consistency check. A nominal discount rate paired with real terminal growth understates the numerator relative to the denominator, while a real discount rate paired with nominal growth narrows the perpetuity denominator artificially. The engine only enforces discount rate greater than terminal growth; that mathematical guard cannot detect a basis mismatch.
Worked example — one real cash flow stream discounted correctly and incorrectly, with the gap between the two present values shown
Consider three hypothetical real cash flows of 100 discounted at a real 5% rate: their present value is 272.32. Inflate them by 2% each year to 102, 104.04 and 106.12, then discount at the exactly matched 7.1% nominal rate, and the value is also 272.32. Discounting the unchanged real stream at 7.1% instead produces 261.95, exposing the inconsistency.
What this does not cover — the calculator does not know which basis you chose and cannot detect a mismatch for you
ToolAcre cannot know whether a number includes inflation. Its pure engine receives decimal growth and discount rates, validates that they are finite and applies them exactly. It does not fetch forecasts, label their price basis or convert a nominal model to a real one. A plausible-looking output therefore does not certify that the inputs share a basis.
Choose one basis before you type anything — how the ToolAcre DCF Calculator keeps every input explicit so the consistency check is yours to make
Write “nominal” or “real” beside the model before entering anything, then translate the complete set rather than changing one rate. The calculator keeps growth, discount and terminal assumptions visible, which makes the audit possible, but the output remains a model determined entirely by the assumptions supplied and is not a correct valuation discovered by the tool.