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WACC explained: how to estimate a discount rate for DCF

A practical guide to WACC: what it is, how to compute it, and how to use it (carefully) as a DCF discount rate.

Updated 2026-02-22
Best for

Finance practitioners estimating a workable discount-rate range for DCF or capital allocation work.

Decision

What discount-rate range is defensible enough to use without hiding the underlying cost-of-capital assumptions.

Use it when

You need to make CAPM, debt-cost, tax, and capital-structure choices explicit before valuing the business.

Reviewed by

MetricKit editorial review for valuation modeling.

Reviewed to keep WACC inputs connected to the downstream DCF and sensitivity pages instead of treating the rate as a black box.

Try it in a calculator

WACC Calculator
Example: 70% equity, 30% debt, 15% cost of equity, 7% cost of debt, 25% tax

What WACC means

WACC (weighted average cost of capital) is the blended required return of capital providers: equity holders and debt holders. Debt is adjusted for taxes because interest is often tax deductible.

Core formula

WACC = w_e*k_e + w_d*k_d*(1 - tax rate)

How to calculate WACC (step-by-step)

  • Estimate market-value weights for equity and debt (w_e and w_d).
  • Estimate cost of equity (k_e), often via CAPM as a starting point.
  • Estimate cost of debt (k_d) from current borrowing rates or comparable issuers.
  • Apply the tax shield: after-tax cost of debt = k_d * (1 - tax rate).
  • Compute WACC using the core formula above.

How to choose inputs (practical)

  • Weights: use market-value capital structure when possible (not book values).
  • Cost of equity: often estimated via CAPM as a starting point (risk-free + beta*equity risk premium).
  • Cost of debt: current borrowing rate for the firm's risk profile.
  • Tax rate: marginal corporate tax rate applicable to interest deductions.

Common mistakes

  • Using WACC for projects with different risk than the business.
  • Using a single-point WACC without sensitivity analysis.
  • Letting terminal value dominate because discount rate is too low.

FAQ

Is WACC the same as discount rate-
WACC is often used as a discount rate proxy for valuing the overall firm. But the correct discount rate should match the risk of the cash flows being discounted.
Should I use after-tax or pre-tax cash flows-
Be consistent. Most DCFs discount after-tax free cash flows and use WACC as an after-tax rate proxy. Mixing pre-tax cash flows with after-tax discount rates can distort valuation.

More in finance

DCF sensitivity analysis: how WACC and terminal growth move valuation
Use this guide when a single DCF output looks too precise. It shows how to build a WACC vs terminal growth grid, choose defensible ranges, and judge whether a valuation is robust enough to use in a decision.
Discount rate: how to choose it for NPV and DCF
A practical guide to discount rates: what they mean, how to choose a rate (WACC vs MARR), and how to avoid common mistakes.
Valuation modeling hub: WACC, DCF, multiples, and equity value
A practical hub for valuation modeling: estimate a discount rate (WACC), run a simple DCF with sensitivity analysis, and translate enterprise value to equity value.
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