WACC Calculator — Weighted Average Cost of Capital

WACC (Weighted Average Cost of Capital) is the blended return a company must pay its investors: WACC = E/(E+D) × Ke + D/(E+D) × Kd × (1 − tax). Enter your equity, debt, cost of equity, cost of debt and tax rate below to compute it instantly.

The weighted average cost of capital is the single most consequential number in a valuation, because every future cash flow is discounted by it — a one-point change can move enterprise value by more than 10%. A company funded by both equity and debt must satisfy both groups of investors, so WACC blends their required returns by how much of each the company uses. Because interest on debt is tax-deductible, debt carries a lower effective cost than equity, which is why capital structure changes the result.

WACC = (E ÷ (E + D)) × Ke + (D ÷ (E + D)) × Kd × (1 − Tax Rate)

Worked example (default inputs)

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Why WACC decides valuations more than any other input

The weighted average cost of capital is the rate every future cash flow gets divided by, so it sits at the centre of almost every valuation. That leverage cuts both ways: because the effect compounds through the discounting, a small error in WACC produces a large error in value. For a business with most of its worth in later years, moving WACC by a single percentage point routinely shifts enterprise value by 10–20%. No revenue assumption you argue about in a board meeting moves the number that much.

The formula, and why the tax shield is in it

WACC blends the returns debt and equity investors require, weighted by how much of each funds the business: WACC = (E ÷ V) × Ke + (D ÷ V) × Kd × (1 − tax rate). E is the market value of equity, D of debt, and V is their sum. The cost of debt carries the (1 − tax) multiplier because interest is deductible — the government effectively subsidises borrowing, which is why debt looks cheaper than equity even before you account for its lower risk. This tax shield is a real driver of value, not an accounting footnote.

A worked blend

Take a company funded 70% by equity and 30% by debt, with a 10.6% cost of equity (from CAPM), a 6% pre-tax cost of debt, and a 25% tax rate. The after-tax cost of debt is 6% × 0.75 = 4.5%. WACC = 0.70 × 10.6% + 0.30 × 4.5% = 7.42% + 1.35% = 8.77%. That single figure now discounts every projected cash flow in the model.

What the research and market data say about the inputs

The inputs are not free parameters to be reverse-engineered until the valuation looks right. Each has an evidence base. Graham and Harvey's landmark survey of chief financial officers found that roughly three-quarters of large-company CFOs use the capital asset pricing model to estimate the cost of equity that feeds WACC — it is the dominant method in practice, not just in textbooks. For the discount rate's components, Aswath Damodaran of NYU Stern publishes cost-of-capital and equity-risk-premium data by sector and country every year, which is the standard external reference professionals calibrate against.

Sources: Graham, J. & Harvey, C. (2001), “The theory and practice of corporate finance”, Journal of Financial Economics; and Damodaran Online — cost of capital by sector.

Typical WACC by sector

As a sanity check rather than a substitute for your own calculation: regulated utilities with stable, contracted cash flows often sit around 6–8%; mature industrials and consumer businesses 8–11%; capital-intensive infrastructure 9–12%; and early-stage or high-risk ventures 15–25%. If your computed WACC lands far outside the range for comparable businesses, an input is usually wrong — most often beta or the capital-structure weights.

Case study: how a WACC error compounds

A private clinic group is being valued on a five-year DCF with a stable terminal value. The analyst uses a 9% WACC and reaches an enterprise value near $14M. A reviewer notices the beta was pulled raw from listed hospital operators without relevering for the target's lighter debt load — the correct WACC is closer to 10.5%. That 1.5-point change, applied through the discounting and a terminal value that carries two-thirds of the total, drops enterprise value to roughly $11.5M. An 18% haircut, from one overlooked adjustment. This is why lenders and buyers read the WACC build before they read the growth line.

When WACC is the wrong tool

WACC assumes a roughly constant capital structure. If leverage will change materially over the forecast — a leveraged buyout paying down debt, or a project drawing then repaying a facility — the adjusted present value method, which values the business unlevered and adds the tax shield separately, is more honest. And WACC belongs with unlevered free cash flow in an enterprise DCF; pairing it with levered cash flow double-counts the debt. Match the rate to the cash flow.

Estimating WACC for a private company

Private businesses have no share price, which complicates two inputs at once: the equity weight and beta. Practitioners work around it in a standard way. Beta is taken from listed comparables, unlevered to remove their financing, then relevered at the private company's own target capital structure. The equity weight uses either a target ratio the company is managing toward or an estimate implied by applying a comparable-company multiple to earnings — sometimes solved iteratively, since the equity value you are trying to find also sets the weight. A size premium is then commonly added to the cost of equity, because small private firms have historically demanded returns above what beta alone predicts. None of these steps is exotic, but skipping them is how a private-company WACC ends up understated and the valuation overstated. A useful sanity check is to back out the WACC that the eventual valuation implies and ask whether a real buyer of a business this size and risk would accept that return — if not, the inputs need another look before the number leaves the room.

From the calculator to a linked model

This calculator gives you the blended rate in seconds. Feeding it through a full valuation — where WACC discounts every projected cash flow and flows into the terminal value — is where the number earns its keep. The generated financial model writes the WACC and CAPM formulas into a linked Excel workbook and connects them straight to the DCF, so the discount rate and the valuation always move together, and free for a 3-year model.

Frequently asked questions

What is a good WACC?

Most established companies fall between 7% and 12%; venture-stage startups are often 18–25% to reflect risk. Capital-intensive infrastructure (solar, telecom, data centers) is typically 9–12%.

Why is the cost of debt after-tax?

Interest is usually tax-deductible, so debt's true cost to shareholders is Kd × (1 − tax rate). A 8% loan at a 21% tax rate effectively costs 6.32%.

Where is WACC used in a financial model?

As the discount rate in DCF valuation — future free cash flows and the terminal value are discounted at WACC to compute enterprise value.

How do I lower my WACC?

Adding modest low-cost debt reduces WACC up to the point where financial risk begins raising the cost of both debt and equity. Beyond that, more leverage increases WACC. The level that minimises it is the optimal capital structure.

What is a good WACC?

There is no universal figure — it depends on risk. Regulated utilities run around 6–8%, mature companies 8–12%, and early-stage ventures 15–25%. The test is relative: your WACC should sit near those of genuinely comparable businesses, and a large gap usually signals a wrong input.

Should I use book or market values for the weights?

Market values. Book equity reflects historical accounting, not what investors would pay today, and using it distorts the weights — often badly for a company whose shares trade well above book. Use market capitalisation for equity and market (or fair) value for debt.

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