Understanding WACC in Private Company Valuation

Understand WACC in private company valuation, including its key components, risk adjustments, capital

WACC works the same way in theory whether a company is listed or private. A blend of the cost of equity and after-tax cost of debt, weighted by capital structure. In practice, private company valuation runs into a series of problems public company valuation simply doesn't face, because almost every standard input WACC relies on assumes an observable, liquid market that a private company doesn't have.

The Beta Problem

CAPM, which drives the cost of equity component of WACC, needs a beta i.e. a measure of how a company's returns move relative to the broader market. A private company has no trading history to calculate this from directly, so there's no way to observe its beta the way there is for a listed peer.

The standard workaround is to borrow beta from comparable listed companies, then "unlever" it to strip out each comparable's own capital structure, average the result, and "relever" it using the private company's actual, or intended, capital structure. This process is reasonable in principle, but every step introduces judgement which companies genuinely qualify as comparable, how to handle a comparable set with wildly different leverage levels, and how to weight comparables that operate in adjacent but not identical business lines.

The Size Premium

A substantial body of empirical research indicates that smaller companies have historically generated higher returns than larger ones, after controlling for other risk factors . A pattern generally attributed to lower liquidity, thinner management depth, and greater vulnerability to a single adverse event. Most private companies being valued are considerably smaller than the listed comparables their beta is being borrowed from, which means a size premium is frequently added to the CAPM-derived cost of equity to correct for this gap.

Getting the size premium right matters more than it might seem, since it can add several percentage points to the discount rate for a genuinely small private company and the specific data source and bucket used to determine the premium can itself produce meaningfully different results.

Company-Specific Risk Premium

Beyond size private companies often carry risks that a market‑derived beta does not capture. Private companies can be focused on a customer or supplier. Private companies may depend on a few key employees. Private companies might have internal financial controls. Private companies can be exposed to one geographic market. A company-specific risk premium is often layered on top of the size-adjusted CAPM result to account for these factors.

This is also where WACC estimation is most vulnerable to being quietly manipulated to produce a lower valuation than the facts support. A company-specific premium must be connected to real risk factors that are actually present, in that business. It should not be treated as a number that gets adjusted just to make the final valuation look better. The premium needs to reflect risks not be shaped to fit a desired outcome.

Capital Structure: Actual vs Target

Public company WACC calculations typically use the company's actual, observable market-value capital structure. A private company does not normally have a market value, for its equity. The equity is the thing that is being calculated which creates a true circularity problem.The common resolution is to use an industry-average or peer-group target capital structure instead of the company's own book-value debt-to-equity ratio, since book value can differ substantially from what the company's true market-value capital structure would actually look like.

Why Getting WACC Wrong Compounds So Heavily

Because the WACC is used to discount cash flows over the projection period and because the terminal value relies heavily on it even a small error in the private company WACC. Like a wrong beta match, an incorrect size premium or an unjustified company-specific risk adjustment. Can lead to a big change, in the final valuation. This is precisely why private company discount rate assumptions deserve more scrutiny, not less, compared to a public company where most of the inputs are directly observable.

Every input that a public company WACC calculation assumes as given. An observable beta, a market-value capital structure, a size and risk profile similar, to the index. Must be estimated, adjusted or put back together for a private company. A defensible private company WACC documents each of these judgment calls explicitly, rather than presenting a single