TL;DR. The weighted average cost of capital (WACC) is the blended return
a company must earn to satisfy both its lenders and its shareholders. It combines the after-tax cost
of debt and the cost of equity, weighted by how much of each the company uses. WACC is the discount
rate in a discounted cash flow (DCF) model and the internal hurdle rate that separates value-creating
projects from value-destroying ones. Get any of the three inputs wrong — the mix, the cost of
equity, or the tax shield — and the whole valuation follows.
Why WACC matters
Every dollar a company invests came from somewhere. Some was borrowed from banks or bondholders,
and those creditors want interest. The rest came from shareholders, who accept ownership in exchange
for an expected return on their capital. WACC is the single number that summarizes what those two
groups collectively demand.
Use cases for WACC:
- DCF valuation. WACC is the discount rate you apply to a firm’s projected free
cash flow to the firm (FCFF) to arrive at enterprise value. Small changes in WACC swing the
output badly — a 1 percentage point WACC change on a growing company can move fair value
by 15–25%. - Capital budgeting. A project earning less than WACC destroys value; a project
earning more creates it. WACC is the hurdle every internal proposal has to clear. - M&A. Buyers use the target’s WACC to value the deal, then compare
to their own to see whether the combined firm becomes cheaper or more expensive to finance. - Regulated industries. Utilities, pipelines, and telcos have their allowed
returns set as a function of WACC by regulators — making the calculation not just
theoretical but rate-case-material.
The formula
The textbook form is:
Reading the pieces:
- E = market value of equity (share price × shares outstanding).
- D = market value of debt (bond market prices, not book value on the balance sheet).
- V = E + D = total capital.
- Re = cost of equity (what shareholders demand).
- Rd = cost of debt (what bondholders receive, i.e. the yield to maturity on the company’s bonds).
- Tc = marginal corporate tax rate.
The (1 − Tc) term is the “tax shield”: interest is
deductible, so every dollar of interest costs the firm only Rd · (1 − Tc)
after tax. Dividends are not deductible, so there is no equivalent shield on the equity side.
Where the inputs come from
Cost of equity via CAPM
Cost of equity is not observable — shareholders don’t send you an invoice. The most common
proxy is the Capital Asset Pricing Model:
Re = Rf + β · ERP
- Rf: the risk-free rate. Almost always the yield on a long-dated
Treasury — typically the 10-year. As of Federal Reserve H.15
on July 30, 2026, the 10-year Treasury constant maturity is 4.67%. - β: the stock’s beta — sensitivity of its returns to the broad market
(S&P 500). A beta of 1.0 moves with the market; 1.5 is 50% more volatile; 0.7 is 30% less. - ERP: the equity risk premium — the extra return investors demand for
holding stocks over Treasuries. Aswath Damodaran’s implied U.S. ERP
as of January 5, 2026 is 4.46%.
Cost of debt
Two clean ways to get it:
- Take the yield to maturity (YTM) on the company’s most recently issued long-dated bond —
that is literally the return new bondholders demand today. - If the company has no publicly traded debt, apply a credit spread to the risk-free rate
based on its credit rating (e.g. BBB corporates trade at roughly x basis points over
Treasuries).
Then subtract the tax shield: Rd · (1 − Tc).
The weights (E/V and D/V)
Use market values, not book. A company whose stock has tripled has a much bigger equity
weight than its balance sheet suggests. Getting this wrong is one of the most common errors in
practitioner WACC calculations.
A worked example
Consider a hypothetical U.S. semiconductor company with the following inputs, using real July 2026
benchmarks:
| Input | Value | Source |
|---|---|---|
| Risk-free rate (10Y UST) | 4.67% | Fed H.15, July 30, 2026 |
| Equity risk premium (US) | 4.46% | Damodaran, Jan 2026 |
| Levered beta (assumed) | 1.30 | Illustrative |
| Pre-tax cost of debt (assumed BBB) | 5.50% | Illustrative, IG range |
| Marginal tax rate | 21% | U.S. statutory federal rate |
| Equity weight (E/V) | 85% | Illustrative |
| Debt weight (D/V) | 15% | Illustrative |
Step 1 — cost of equity:
Re = 4.67% + 1.30 × 4.46% = 4.67% + 5.80% = 10.47%
Step 2 — after-tax cost of debt:
Rd · (1 − Tc) = 5.50% × (1 − 0.21) = 5.50% × 0.79 = 4.35%
Step 3 — blend:
WACC = 0.85 × 10.47% + 0.15 × 4.35% = 8.90% + 0.65% = 9.55%
A WACC of ~9.5% is close to what Damodaran’s data services observe for the U.S. semiconductor
sector (10.55% across 66 firms as of January 2026) — a useful sanity check.
Sector WACCs — a data snapshot
WACC varies dramatically by industry because equity risk (beta), debt capacity, and tax posture
all vary. Damodaran publishes an updated dataset for U.S. industries every January. A cross-section:
| Industry | WACC | Firms in sample |
|---|---|---|
| Semiconductor | 10.55% | 66 |
| Semiconductor Equipment | 9.89% | 31 |
| Retail (Building Supply) | 9.51% | 14 |
| Auto & Truck | 9.38% | 33 |
| Software (System & Application) | 9.34% | 309 |
| Electrical Equipment | 8.99% | 112 |
| Engineering & Construction | 8.69% | 48 |
| Construction Supplies | 8.29% | 40 |
| Computer Services | 7.83% | 64 |
| Aerospace & Defense | 7.60% | 79 |
| Total U.S. market | 6.96% | 5,994 |
| Total ex-financials | 7.72% | 4,822 |
Visualized as a bar chart:
Two things to notice. First, sector spread is wide: 3 full percentage points separates the top of
the list from the bottom, which translates into meaningfully different valuations for otherwise
similar cash flow streams. Second, the total-market number is lower than most individual
sectors because of the huge weight of financial firms and utilities, which run WACCs well below 7%.
Common mistakes
- Using book weights instead of market weights. A stock at 2x book gets its
equity weight understated if you use the balance sheet, which inflates WACC and understates
valuation. - Ignoring the tax shield on debt. Forgetting the
(1 − Tc)
term inflates the debt cost and, again, WACC. - Applying the same WACC to a division with different risk. A conglomerate’s
corporate WACC is not the right hurdle rate for a startup subsidiary in a completely different
industry. Use divisional betas. - Using the current 3-month T-bill as Rf. Cash flows in a DCF stretch
out 10+ years; match the risk-free rate to that horizon (10-year Treasury is standard). - Not levering / unlevering beta. A comparable company’s beta reflects its
capital structure. To use it on a company with a different D/E, unlever it, then relever at
your target ratio. - Double-counting country risk. Adding a country risk premium to the ERP
and haircutting the projected cash flows is counting the same risk twice. - Using stale weights during a market move. After a stock has fallen 40%, the
equity weight in WACC has fallen with it — the D/V is now much higher, and so is the
calculated WACC. Refresh weights before valuing.
When WACC breaks down
WACC assumes a stable capital structure and reasonably diversified equity holders. It is a poor
tool when either assumption fails:
- Distressed firms. If bankruptcy is a real probability, cost of debt and cost
of equity both spike and become path-dependent. Use adjusted present value (APV) or scenario
trees instead. - Private, undiversified owners. A single-owner private business can’t just look
up beta on Yahoo Finance; the owner bears idiosyncratic risk that a diversified public investor
doesn’t. Some private-company practitioners use a total-beta approach (beta / correlation to
market) to compensate. - Rapidly changing leverage. An LBO target’s D/V shrinks quickly as debt gets
paid down. Use APV, which values the unlevered firm and the tax shields separately, rather
than a single stale WACC. - Very early-stage companies. When there are no meaningful cash flows for
several years, the WACC-based DCF becomes overwhelmingly a terminal-value calculation. VC
practitioners typically switch to explicit exit-value methods or the venture-capital method.
Related concepts to learn next
- DCF valuation —
WACC is the discount rate that DCF uses. - Beta, alpha and CAPM —
the model that supplies the cost of equity. - Investment grade vs high yield —
credit rating drives the cost of debt. - Leveraged buyouts —
a classic case where WACC alone is not the right lens; APV replaces it.
Sources
- Damodaran, Cost of Capital by Industry (US), NYU Stern, January 2026
- Damodaran, Country Equity Risk Premiums, NYU Stern, January 5, 2026
- Federal Reserve H.15 — Selected Interest Rates (July 29–30, 2026)
- Modigliani, F. and Miller, M. (1958, 1963), foundational papers on capital structure and the tax shield.
Disclosure: This article was produced with AI assistance and reviewed before publication. It is for informational purposes only and is not investment advice.