WACC: Formula, Calculation, PME Examples and Common Pitfalls (France 2026)

Last updated: 15 May 2026.

The WACC (Weighted Average Cost of Capital) is the rate at which future cash flows are discounted to estimate a company's present value today. It represents the minimum return a business must generate to remunerate both its shareholders and its creditors. Getting the WACC right is the cornerstone of any serious DCF valuation.

Quick answer. WACC combines the cost of equity (estimated via CAPM) and the after-tax cost of debt, weighted by their respective share of total financing. For an established French SME, the typical range is 8-13%. For a startup, 15-25%. Each 1-point difference in WACC can shift a DCF valuation by 10-20%, depending on the projection horizon.

A company is financed through two main sources: equity (capital contributed by shareholders, retained earnings, share premium) and financial debt (bank loans, bonds, leasing, remunerated shareholder current accounts). Each carries a cost:

• Shareholders expect a return that compensates for the risk taken. This return is implicit — it does not appear in the income statement, but it exists.
• Creditors require an interest rate. This cost is explicit and — a fiscal advantage — interest is deductible from corporate income tax.

WACC weights these two costs by their relative importance in the financial structure. It is the "profitability hurdle" that any investment must clear to be value-creating.

In practice, WACC appears in three situations:

1. DCF valuation: the company — or an acquirer — projects free cash flows (FCF) over 5-10 years, then discounts them at the WACC to obtain the Enterprise Value.
2. Investment decision: the IRR (Internal Rate of Return) of a project is compared to the WACC. If IRR > WACC, the project creates value.
3. Profitability benchmarking: ROIC (Return on Invested Capital) is compared to WACC to measure whether the company creates or destroys value each year.

$$WACC = \frac{E}{V} \times Re + \frac{D}{V} \times Rd \times (1 - t)$$

The (1 - t) term is critical: it captures the tax shield on interest payments. At a 25% corporate tax rate, a 5% gross debt costs only 3.75% after tax.

The CAPM (Capital Asset Pricing Model) is the standard model for estimating Re:

$$Re = Rf + \beta \times (Rm - Rf)$$

3.1 The risk-free rate Rf#

The risk-free rate is conventionally the yield on the 10-year French government bond (OAT). As of mid-2025, this rate was around 3.0-3.5% (source: Banque de France — to be verified at the time of calculation, as it fluctuates with ECB monetary policy).

3.2 The equity risk premium (Rm - Rf)#

The equity risk premium represents the additional return investors demand for holding equities rather than a risk-free asset. For France, Damodaran (NYU Stern) estimates it at between 5.5% and 7%, depending on the period and methodology (geometric vs arithmetic, historical vs implied). In practice, French practitioners often use 6-7% for 2025-2026 valuations (to confirm with the source used).

3.3 Beta: systematic risk of the company#

Beta measures the sensitivity of a company's returns to market movements:

• Beta = 1: risk equal to the market
• Beta < 1: less volatile company (e.g. food distribution)
• Beta > 1: more volatile company (e.g. technology, biotech)

For an unlisted company, beta cannot be directly observed. The standard approach:

1. Select a panel of comparable listed companies (same sector, comparable size as much as possible)
2. Retrieve their levered beta (observed market beta, which includes the effect of financial leverage)
3. Unlever the beta (Hamada formula) to obtain the pure economic beta:

$$\beta_{unlevered} = \frac{\beta_{levered}}{1 + (1 - t) \times \frac{D}{E}}$$

1. Re-lever this beta using the target leverage of the company being valued:

$$\beta_{levered\ target} = \beta_{unlevered} \times \left(1 + (1 - t) \times \frac{D_{target}}{E_{target}}\right)$$

1. Calculate Re with this re-levered beta

The cost of debt appears simpler: it is the weighted average interest rate the company pays on all its financial liabilities (long/short-term loans, leasing, bonds, remunerated current accounts).

Common pitfalls:

• Using the historical rate of a loan contracted 10 years ago does not reflect the current cost of debt
• Excluding off-balance-sheet debt or finance lease obligations is a common error in SME files
• The cost of debt should be the rate "achievable today" on the market, not a rate negotiated under exceptional conditions

For a French SME in 2025-2026, a gross Rd between 3.5% and 6% is a reasonable range depending on the risk profile and balance sheet quality (to be verified against current market conditions).

This is one of the most debated questions in practice. The theoretical WACC formula uses market values of debt and equity, not book values.

For valuing an unlisted SME, one typically observes the current leverage and compares it to the sector median to determine whether the company is moving towards or away from it. If the company is rapidly deleveraging, the target leverage will differ significantly from today's observed leverage — and the WACC should in principle be recalculated each year (which APV handles more cleanly).

These ranges are indicative and based on mid-2025 market parameters. They must be recalibrated for each specific valuation.

DCF valuation#

A DCF valuation follows five steps:

1. Project FCF (free cash flows after investments) over 5-10 years
2. Estimate a terminal value (Gordon-Shapiro or exit multiple)
3. Discount everything at the WACC to obtain Enterprise Value (EV)
4. Subtract net debt to obtain Equity Value
5. Divide by the number of shares or units to obtain the per-share price

Critical sensitivity: A WACC of 10% vs 12% on a project with stable FCF of EUR 1M/year over 10 years produces valuations of EUR 6.1M vs EUR 5.6M — an 8% gap. For high-growth projects (startups, infrastructure), the gap is much larger because the terminal value carries far more weight.

IRR vs WACC: the decision rule#

• IRR > WACC: the project creates value; the investment is attractive
• IRR = WACC: the project exactly covers the cost of capital; zero NPV
• IRR < WACC: the project destroys value; avoid unless exceptional strategic reasons

A French B2B SaaS startup founded in 2021, generating EUR 5M ARR with 40% annual growth, 115% net revenue retention, MRR churn below 2%, and negative EBITDA of -EUR 1.5M. It is preparing a Series B fundraise.

WACC parameters:

Indicative valuation: If one projects positive FCF from year 3 reaching EUR 2M in year 5, with a 3% perpetual growth rate in the terminal value, the DCF valuation at a 17% WACC will be significantly lower than a market SaaS multiple (ARR x 5-8). This gap explains why Series B investors often prefer revenue multiples over DCF to value high-growth startups: DCF heavily penalises distant cash flows.

Our read on this file: the founder must understand that the higher the WACC, the less future cash flows are worth today. Reducing perceived risk — through MRR quality, customer diversification, revenue predictability — is just as important as accelerating growth for improving DCF valuation.

Core limitations#

Constant leverage assumption. WACC assumes the D/V ratio remains stable throughout the projection period. In reality, companies repay debt, make acquisitions, or recapitalise. Each leverage change should theoretically require recalculating the WACC for that period.

Ill-suited to unlisted SMEs. Beta is a market concept. An unlisted SME has no observable beta. Estimation from comparables introduces bias if the listed companies differ significantly in size, liquidity, or geography. It is common to add a "specific premium" (illiquidity, key-person dependence, customer concentration) of 2-5 additional points for SMEs.

Single WACC for a specific project. If a diversified company evaluates a project in a sector very different from its core business, the corporate WACC is not the right rate: a project risk-adjusted WACC is needed.

Practical alternatives#

Pitfall 1: Beta not adjusted for leverage#

Using the levered beta of a large listed company (e.g. Capgemini to value a 20-person IT services firm) without proceeding with the unlever/re-lever Hamada adjustment. The listed company's levered beta reflects its own financial leverage, not that of the target being valued.

Pitfall 2: Generic risk premium without SME-specific premium#

Applying a market risk premium without adding an SME-specific premium systematically underestimates WACC for small structures. An SME with EUR 5M turnover where a single client represents 60% of revenue does not have the same risk profile as a broad equity index.

Pitfall 3: Frozen risk-free rate#

Using an Rf calculated in 2021 (near-zero rates) in a file drafted in 2025 massively biases the WACC downwards. Rf must be updated to the valuation date.

Pitfall 4: Book values instead of market values#

In France, book equity for an SME includes accumulated reserves and retained earnings since inception. Market value of equity can differ substantially — particularly for companies with significant uncapitalised intangible assets (customer base, brand, internal R&D). Using book equity to weight the WACC means applying the right rate to the wrong base.

When Cabinet Hayot Expertise accompanies an SME or startup in a DCF valuation — whether for a fundraise, sale, or acquisition — the first control points focus on:

1. Consistency of Rf with the valuation date and the source (Banque de France, ECB)
2. Relevance of the comparables panel for beta: same sector, European geography preferred
3. Existence of an explicit, documented SME-specific premium where applicable
4. Leverage used for weighting: market value or book value, and how it was estimated
5. Model sensitivity: a WACC +/- 2 points table is systematically requested to show the valuation range

A WACC that is too low is just as dangerous as one that is too high. In the first case, the company is overvalued, creating poor entry conditions for the investor. In the second, the founder cedes too much value.

The underestimated risk: SME founders tend to reuse the WACC calculated during a previous fundraise without updating it. Between a 2021 valuation (zero rates, high SaaS multiples) and 2025 (normalised rates, compressed multiples), WACC may have increased by 5-8 points — which radically changes the DCF valuation.

• OAT 10-year: monitor ECB policy evolution and its impact on the risk-free rate. Each basis point rise in Rf flows directly into Re and WACC.
• Equity risk premium: Damodaran updates his estimates annually. Do not use a version prior to 2024 for a 2025-2026 file.
• Sector beta: technology sector betas have declined significantly since the 2021-2022 peaks. A SaaS beta used in 2021 overstates systematic risk today.
• Corporate tax rate: France's standard IS rate is 25% since 2022. The reduced SME rate (15% on the first EUR 42,500 of profit, to be confirmed) may apply for eligible structures — slightly modifying the debt tax shield.

• Rf updated to valuation date (Banque de France source)
• Equity risk premium from a recent source (Damodaran, BDO, KPMG)
• Comparables panel documented (sector, country, leverage)
• Beta unlevered then re-levered to target leverage
• SME-specific premium explicitly justified if applicable
• Rd based on current market rate, not a historical rate
• Weighting on market values (or justification of book value approximation)
• Sensitivity table WACC +/- 2 points produced
• Consistency between WACC and valuation method (DCF / APV / multiples)

• Banque de France - OAT 10-year rate: https://www.banque-france.fr
• Damodaran NYU - Equity Risk Premiums and European Betas: https://pages.stern.nyu.edu/~adamodar/
• INSEE - Corporate financial results (FARE database): https://www.insee.fr
• BPI France - SME financing guide: https://www.bpifrance.fr
• AMF - Methodology for valuing unlisted companies: https://www.amf-france.org

This article is provided for informational purposes. Calculating a WACC for a specific valuation requires analysis of the financial documents, market conditions at the valuation date, and the particular situation of the company. Cabinet Hayot Expertise provides personalised support on these matters.