WACC: Weighted Average Cost of Capital Explained

The weighted average cost of capital (WACC) is one of the most important concepts in corporate finance. It represents the average rate a company pays to finance itself, and it's used as the benchmark for investment decisions and valuation. This guide explains what WACC is, the formula, how its components are calculated, how it's used, and why it matters — in plain language. It's a core topic in corporate finance, central to ACCA and finance study.

What is WACC?

A company raises money from two main sources: equity (from shareholders) and debt (from lenders). Each has a cost — shareholders expect returns, and lenders charge interest. The weighted average cost of capital is the average of these costs, weighted by how much of each the company uses. In other words, WACC is the overall rate of return a company must earn on its assets to satisfy all its providers of finance. It's effectively the company's blended "cost of money."

The WACC formula

WACC is calculated as:

WACC = (E/V × Re) + (D/V × Rd × (1 − Tc))

Where E is the market value of equity, D is the market value of debt, V is the total (E + D), Re is the cost of equity, Rd is the cost of debt, and Tc is the corporate tax rate. The E/V and D/V terms are simply the proportions of equity and debt in the financing mix, used to weight each cost accordingly.

The components

Two costs feed into WACC:

• Cost of equity (Re). The return shareholders require. It's often estimated using the Capital Asset Pricing Model (CAPM), which builds it up from the risk-free rate plus a premium for the share's risk (its beta).
• Cost of debt (Rd). The effective interest rate the company pays on its borrowings. Crucially, it's adjusted for tax — because interest is usually tax-deductible, the after-tax cost of debt is lower, which is why the formula multiplies it by (1 − Tc).

This tax shield is why debt is often a relatively cheap source of finance.

A worked example

Suppose a company is financed 60% by equity and 40% by debt. Its cost of equity is 10%, its cost of debt is 5%, and the tax rate is 20%. The after-tax cost of debt is 5% × (1 − 0.20) = 4%. The WACC is then (0.60 × 10%) + (0.40 × 4%) = 6% + 1.6% = 7.6%. So this company needs to earn at least 7.6% on its investments just to cover the cost of its financing — anything above that creates value for investors.

How WACC is used

WACC has two main uses. First, as a discount rate: in investment appraisal, future cash flows from a project are discounted back to present value using WACC, and in discounted cash flow valuation, WACC discounts a company's projected cash flows to estimate its value. Second, as a hurdle rate: a project is generally only worthwhile if its return exceeds the company's WACC — otherwise it destroys value, because it's not even covering the cost of the money used to fund it.

Why WACC matters

WACC matters because it is the key link between financing and investment. A company that earns more than its WACC creates value for its investors; one that earns less destroys it. A lower WACC means cheaper financing and a lower hurdle for projects, making more investments viable — which is why companies think carefully about their mix of debt and equity. For anyone in finance, WACC underpins valuation, capital budgeting and capital-structure decisions, making it one of the most important numbers in corporate finance.

Why WACC matters in practice

WACC is widely used as the discount rate in investment appraisal and business valuation, because it reflects the average return a company must earn to satisfy all its providers of capital. A project expected to return more than the WACC creates value; one returning less destroys it. Because WACC blends the cost of equity and the after-tax cost of debt, weighted by their proportions in the capital structure, it is sensitive to assumptions — small changes in inputs can materially shift the result, so it should be used with judgement rather than treated as a precise figure.

Frequently asked questions

What is WACC?

The weighted average cost of capital — the average rate a company pays to finance itself, blending the cost of equity and the cost of debt, weighted by their proportions in the financing mix.

What is the WACC formula?

WACC = (E/V × Re) + (D/V × Rd × (1 − Tc)) — combining the cost of equity and the after-tax cost of debt, weighted by the proportions of equity and debt in the capital structure.

Why is the cost of debt adjusted for tax?

Because interest is usually tax-deductible, the effective (after-tax) cost of debt is lower than the headline interest rate — the "tax shield" — which the (1 − Tc) term captures.

How is WACC used?

As a discount rate for investment appraisal and valuation, and as a hurdle rate — a project should generally earn more than WACC to create value.

Build your corporate-finance skills with Learnsignal

WACC is a cornerstone of corporate finance. Learnsignal's tutor-led ACCA and CIMA courses develop the financial-management understanding that topics like this build on — with clear teaching and exam-focused practice.