What Is the Weighted Average Cost of Capital?

The weighted average cost of capital is the blended rate a company pays for the money it uses, whether that money came from shareholders or lenders. Each source of capital has its own required return — shareholders demand more because they bear the residual risk, lenders demand less because they are paid first and hold collateral — and WACC weights those requirements by how much of each the company actually uses.

WACC matters because it is the hurdle every investment must clear. A project earning 9% when the company's WACC is 8.9% creates almost no value; the same project earning 14% creates a great deal. Without a WACC figure, "profitable" is a meaningless word — a company can report accounting profits while destroying value if it fails to cover the cost of the capital it employs.

How It Works

The formula multiplies each component's cost by its share of total capital and adds the results. Equity cost is used as-is, because dividends are not deductible. Debt cost is reduced by one minus the tax rate, because interest payments are deducted from taxable profit, so the government absorbs part of the bill: a 6% coupon with a 21% tax rate costs 4.74% after tax. Preferred stock sits in between — it is a preferred claim but its dividends receive no tax shield.

In the default example, $300 million of equity at 11%, $150 million of debt at 6% pre-tax and $20 million of preferred at 8% give weights of 63.8%, 31.9% and 4.3%. Equity contributes 7.02 points, debt 1.51 points after tax and preferred 0.34 points, producing a WACC of about 8.87%. The annual capital charge — WACC multiplied by total capital — is roughly $41.7 million, the operating profit needed simply to cover the cost of the money.

The cross-check panel estimates the cost of equity independently using CAPM: risk-free rate plus beta times the equity risk premium. Comparing that figure with the cost of equity you entered is a useful sanity check, because a large gap usually means one of the inputs — beta, the premium, or the company's cost of equity — is out of line with the others.

Understanding Your Results

The primary card shows the WACC with the dollar value of the annual capital charge. The three statistics beside it give the equity weight, the after-tax cost of debt and the CAPM equity estimate. The table breaks the calculation into components, showing each one's value, weight, cost and contribution to the final rate — which makes it obvious which component is driving the result.

Summary Statistics adds the capital mix, the debt-to-equity ratio, the levered beta and the split of the capital charge between equity and debt. Two experiments are worth running. First, increase debt and watch WACC fall initially, as cheaper debt replaces expensive equity, before risk considerations push the equity cost up again. Second, change the tax rate and watch only the debt component move, which demonstrates exactly how much of the debt subsidy comes from the tax code.