The relevant cost of debt for WACC calculations is the interest rate on new debt, not the rate on existing debt, because WACC measures the marginal cost of raising additional capital.
Is cost of debt the same as interest rate?
No, the cost of debt isn't identical to the interest rate, though it’s closely related. The cost of debt includes the interest rate plus any fees or discounts tied to issuing debt, adjusted for tax benefits.
Take a 5% loan with $500 in origination fees on a $10,000 loan—suddenly that 5% jumps to 5.5% before taxes. After the 21% corporate tax deduction (as of 2026), the after-tax cost drops to about 4.35%.
How does cost of debt affect WACC?
The cost of debt directly lowers WACC, because debt is typically cheaper than equity thanks to the tax shield and lower risk to investors.
Here’s a quick example: a company with 40% debt at 4% cost and 60% equity at 10% cost has a WACC of 7.6%. Bump that debt cost to 6%, and WACC climbs to 8.4%. More debt (within reason) can keep lowering WACC—until financial risk gets out of hand.
What is the relevant cost of debt for a corporation?
The relevant cost of debt for WACC is the after-tax cost of new debt, calculated as the yield to maturity on new bonds or loan rates, multiplied by (1 – tax rate).
Say a company issues new 10-year bonds at 5% interest with a 21% corporate tax rate. The after-tax cost? 5% × (1 – 0.21) = 3.95%. That’s the number plugged into WACC—not the old debt’s interest payments.
How do you calculate cost of debt for WACC?
Estimate the yield on new debt, then multiply by (1 – tax rate). That gives the after-tax cost used in the WACC formula.
Imagine a company can issue new bonds at a 6% yield with a 21% tax rate. The after-tax cost of debt? 6% × (1 – 0.21) = 4.74%. Multiply that by the debt’s share of the capital structure, and you’ve got your WACC.
What is the price paid to borrow debt capital called?
The price paid to borrow debt capital is called the interest rate, the percentage charged on the principal over a specific period.
Think of a $100,000 loan at 4% annual interest. That’s $4,000 per year in interest. The rate could be fixed or variable, and lenders might tack on extra fees like origination or commitment charges.
What is a good WACC?
A “good” WACC is typically 2–3% below the company’s return on invested capital (ROIC), though it varies wildly by industry.
Utilities and REITs often land in the 5–7% range, while tech and biotech firms might see 10–15% due to higher risk. The average S&P 500 WACC in 2025? About 8.2%. If WACC exceeds ROIC, the company’s destroying value.
Which is the most expensive source of funds?
The most expensive source of funds is issuing new common stock, followed by retained earnings, then debt.
According to Investopedia, the cost of new equity for most U.S. companies runs 12% to 20%, compared to 4% to 8% for debt. Equity investors demand higher returns because they take on more risk and get no tax breaks.
How cost of debt is calculated?
Add up annual interest expenses, divide by total debt, then adjust for taxes. That gives the effective interest rate across all debt instruments.
Say a company pays $120,000 in annual interest on $3,000,000 in debt. The pre-tax cost is 4%. After a 21% tax rate, the after-tax cost drops to 3.16%. Plug that into financial models and WACC calculations.
How do you calculate interest on a debt?
Divide the annual interest rate by 12, then multiply by the outstanding balance. That’s your monthly interest payment.
Take a $50,000 loan at 6% annual interest. Monthly rate? 0.5%. If you pay $1,000 per month, the first month’s interest is $50,000 × 0.005 = $250. The rest goes to principal.
When should WACC not be used?
WACC shouldn’t be used for highly risky projects, early-stage ventures, or when capital structure is unstable.
Imagine a startup with no debt and shaky cash flows. Using its current WACC to evaluate a new biotech R&D project? Not ideal. A higher discount rate (say, 15–25%) that reflects project-specific risk makes more sense. WACC also falls apart in financial distress, when debt costs spike due to default risk.
Does WACC reduce debt?
No, WACC doesn’t reduce debt—it measures the cost of carrying it. A lower WACC means cheaper capital, which might encourage more borrowing, but it’s a measuring stick, not a debt-reduction tool.
Say a company cuts WACC from 10% to 8% by boosting debt from 30% to 50% of capital. That means the marginal cost of capital fell. But total debt? That depends on cash flow, profitability, and financing choices—not WACC itself.
What are the disadvantages of debt financing?
Debt financing has some serious drawbacks: mandatory payments, restrictive covenants, collateral risk, and cash flow strain during downturns.
- Mandatory payments: Principal and interest must be paid on time, no excuses.
- Covenants: Lenders can limit dividends, asset sales, or additional borrowing.
- Collateral risk: Default? You could lose assets pledged as security.
- Cash flow pressure: High leverage leaves little room to maneuver when revenue dries up.
Picture a restaurant chain with high lease obligations and seasonal revenue. A slow winter season could make those monthly loan payments a real struggle.
Why is debt cheaper than equity?
Debt is cheaper mainly because interest is tax-deductible, slashing the effective cost, and lenders get repaid before shareholders.
In the 21% tax bracket, $1 of interest saves $0.21 in taxes, cutting the real cost to $0.79. Equity investors? They expect 10–20% returns because they take on all the leftover risk with no tax shield. Plus, debt has a contractual claim, making it far less risky than equity.
Does WACC increase with debt?
WACC initially falls as debt rises thanks to the tax shield, but eventually climbs as financial risk grows.
Picture a U-shaped WACC curve. At low debt levels (say, 20%), WACC is high because equity is expensive. Moderate debt (40–60%) lowers WACC via cheaper debt and tax perks. Push past 60–70%, and WACC starts climbing again as both debt and equity costs spike under the weight of bankruptcy risk.
Which is more relevant pretax or after-tax cost of debt?
The after-tax cost of debt matters most for WACC and financial decisions, because it reflects the true cost after tax deductions.
Take a 5% interest rate with a 21% tax rate. The after-tax cost? 3.95%. That’s what goes into WACC formulas and capital budgeting. The pre-tax cost? Useful for calculating interest expense, but not for valuing the company or judging project viability.
