How Interest Rates Flow Into a Company's Cost of Capital
Direct Answer
A company's cost of capital rises directly with the risk-free rate: CAPM prices the cost of equity as the risk-free rate plus beta times the equity risk premium, so a rising Treasury yield lifts the cost of equity dollar-for-dollar holding beta and the risk premium constant. At the same time, corporate bond yields — a company's actual cost of debt — are priced as the Treasury yield plus a credit spread, so they rise alongside Treasury yields too. Because the weighted average cost of capital (WACC) blends both legs, a rising-rate environment pushes WACC up from both sides at once, raising the hurdle rate that capital projects and acquisitions must clear and making fewer of them worth funding.
Key Takeaways
- CAPM ties the cost of equity directly to the risk-free rate: Cost of equity equals the risk-free rate plus beta multiplied by the equity risk premium. A 1 percentage point rise in the risk-free rate raises the cost of equity by exactly 1 percentage point, holding beta and the equity risk premium constant.
- WACC blends cost of equity and after-tax cost of debt, weighted by capital structure: WACC equals the equity weight times the cost of equity, plus the debt weight times the after-tax cost of debt. It is the single discount rate companies apply to evaluate whether a project or acquisition creates value.
- Corporate bond yields rise alongside Treasury yields, compounding the effect: A corporate bond's yield is the comparable Treasury yield plus a credit spread, so the cost-of-debt leg of WACC rises alongside the cost-of-equity leg — not instead of it.
- A higher WACC is a higher hurdle rate: WACC is the discount rate applied to a project's expected cash flows. Raising it lowers the present value of every future cash flow, so fewer projects clear the bar for a positive net present value.
- Higher hurdle rates can slow capex, buybacks, and M&A economy-wide: When the average project has to clear a higher return threshold to be worth funding, corporate investment spending and deal activity both tend to slow, independent of any change in the underlying business opportunities themselves.
- Duration matters here too: Companies whose expected cash flows sit further in the future feel a WACC increase more acutely than companies with near-term cash flows — see Discount Rates and Equity Duration for the mechanics of that sensitivity.
Core Concepts
What Is CAPM and How Does the Risk-Free Rate Set the Cost of Equity?
The Capital Asset Pricing Model (CAPM) is the standard formula analysts use to estimate a company's cost of equity — the return shareholders require to hold the stock, given its risk. The formula is: cost of equity = risk-free rate + beta × equity risk premium. The risk-free rate is normally proxied by the 10-year Treasury yield, since it represents the return available with effectively no default risk. Beta measures the stock's sensitivity to broad market moves (a beta of 1.2 means the stock tends to move about 20% more than the market in either direction), and the equity risk premium is the extra return investors demand for holding stocks over Treasuries.
Because the risk-free rate enters CAPM as a direct additive term rather than a scaled multiplier, a 1 percentage point rise in the 10-year Treasury yield raises the cost of equity by exactly 1 percentage point, holding beta and the equity risk premium constant. This is the cleanest, most direct channel through which Treasury yields feed into corporate valuation and capital-allocation decisions — see the U.S. Department of the Treasury's daily Treasury par yield curve rates for the underlying risk-free rate data.
What Is WACC and How Does It Blend the Cost of Equity and the Cost of Debt?
The weighted average cost of capital (WACC) is the blended rate of return a company must generate across all of its financing sources — equity and debt — to avoid destroying value for either group of investors. The formula weights each financing source by its share of the company's total capital: WACC = (equity weight × cost of equity) + (debt weight × after-tax cost of debt). The cost of debt is taxed down because interest payments are tax-deductible, so the effective after-tax cost to the company is the pretax yield multiplied by (1 − tax rate).
WACC matters because it is the single number companies use as the discount rate in valuation models and as the minimum acceptable return for new investment. A rising risk-free rate raises both inputs to the blend simultaneously — the cost of equity through CAPM, and the cost of debt through corporate bond yields tracking Treasury yields — so WACC does not just drift up from one side, it moves up from both legs at once.
Why Does a Higher WACC Raise the Hurdle Rate for Corporate Investment?
Companies evaluate capital projects and acquisitions by discounting the investment's expected future cash flows back to today at the company's WACC and comparing that present value to the upfront cost — the net present value (NPV) test. WACC functions directly as the hurdle rate: a project only gets funded if its expected return clears the WACC bar. Raising the discount rate mechanically lowers the present value of every future cash flow, and the effect compounds for cash flows further out in time.
The practical consequence is that the same set of potential projects — with unchanged expected cash flows — produces fewer approvals at a higher WACC than at a lower one. This is the direct transmission channel from rising Treasury yields to slower corporate capital expenditure, fewer stock buybacks funded with debt, and reduced M&A activity, since fewer deals clear the higher return bar acquirers now require.
How Do Corporate Bond Yields Rise Alongside Treasury Yields?
A corporate bond's yield is priced as the comparable-maturity Treasury yield plus a credit spread that compensates bondholders for the issuer's default risk relative to the U.S. government, which is treated as the risk-free benchmark. When Treasury yields rise, the Treasury component of every corporate bond's yield rises with it, even if the market's assessment of the issuer's credit quality — and therefore its spread — does not change at all. This means a company's actual, observable cost of debt (what it pays to issue new bonds or refinance maturing debt) rises directly alongside the risk-free rate, not just the theoretical cost of equity from CAPM.
This is why a rising-rate environment compounds rather than offsets the WACC increase: the cost-of-equity leg rises through CAPM, and the cost-of-debt leg rises through the bond market's Treasury-plus-spread pricing convention, at the same time. Credit spreads can widen or narrow independently based on default risk and market conditions, adding a second variable on top of the Treasury base rate — see Rate-Sensitive Industries: Winners and Losers for how this plays out differently across heavily indebted sectors.
Worked Example: Cost of Capital at a 3% vs. 5% Risk-Free Rate
All figures below are simplified, illustrative numbers built to isolate the risk-free-rate-to-WACC mechanism. They are not forecasts or claims about any real company.
- Setup: A hypothetical company has a beta of 1.2, faces a 6% equity risk premium, is financed 70% equity / 30% debt, pays a 25% tax rate, and borrows at the Treasury yield plus a 2 percentage point credit spread.
- Cost of equity at a 3% risk-free rate: 3% + (1.2 × 6%) = 3% + 7.2% = 10.2%.
- Cost of equity at a 5% risk-free rate: 5% + (1.2 × 6%) = 5% + 7.2% = 12.2% — a full 2 percentage point rise, matching the risk-free rate move exactly.
- Cost of debt at a 3% risk-free rate: pretax cost of debt = 3% + 2% spread = 5%; after-tax = 5% × (1 − 0.25) = 3.75%.
- Cost of debt at a 5% risk-free rate: pretax cost of debt = 5% + 2% spread = 7%; after-tax = 7% × (1 − 0.25) = 5.25%.
- WACC at a 3% risk-free rate: (0.70 × 10.2%) + (0.30 × 3.75%) = 7.14% + 1.125% = 8.265%, rounded to 8.27%.
- WACC at a 5% risk-free rate: (0.70 × 12.2%) + (0.30 × 5.25%) = 8.54% + 1.575% = 10.115%, rounded to 10.12%.
- Project impact: A hypothetical project costs $100 million upfront and generates $9 million per year in perpetuity. At an 8.27% WACC, its present value is $9M ÷ 0.0827 ≈ $108.8 million, for a positive NPV of about $8.8 million — the project clears the hurdle. At a 10.12% WACC, the same project's present value falls to $9M ÷ 0.1012 ≈ $88.9 million, for a negative NPV of about $11.1 million — the identical project now destroys value and would not be approved.
- Takeaway: The 2 percentage point rise in the risk-free rate produced a 1.85 percentage point rise in WACC (8.27% to 10.12%) — slightly less than one-for-one only because the after-tax cost-of-debt leg is scaled down by the tax shield, but the direction and magnitude are large enough to flip a real project from value-creating to value-destroying with no change to its underlying cash flows.
Measurement Framework
| Measurement | Question to Answer |
|---|---|
| 10-year Treasury yield (DGS10 on FRED) | What is the current risk-free rate input to CAPM's cost-of-equity formula? |
| Company beta (5-year monthly regression vs. a broad index) | How sensitive is this specific stock to the risk-free-rate-driven cost-of-equity channel? |
| Implied or historical equity risk premium (Damodaran's published ERP series is a common reference) | What extra return are investors currently demanding for holding equities over Treasuries? |
| Company's outstanding bond yields or credit default swap spread | What credit spread is the market pricing on top of the Treasury base rate for this issuer's debt? |
| Disclosed or implied capital structure (debt ÷ total capital, from the balance sheet) | How much weight does the cost-of-debt leg carry in this company's WACC blend? |
| Company's disclosed hurdle rate or discount rate (investor presentations, 10-K capital allocation discussion) | Has management already adjusted its stated investment threshold for the current rate environment? |
Common Failure Modes
Assuming a Static Equity Risk Premium and Beta Over Long Horizons
The worked example above holds beta and the equity risk premium constant to isolate the risk-free-rate channel, but both can shift independently in a real rate cycle — beta can change as a company's leverage or business mix evolves, and the equity risk premium tends to rise during periods of market stress and fall during periods of confidence. Treating CAPM's other two inputs as fixed while only the risk-free rate moves is a useful teaching simplification, not a claim that they stay constant in practice. A rate rise accompanied by a falling equity risk premium (improving investor confidence) can partially offset the mechanical cost-of-equity increase described here.
Confusing the Risk-Free Rate Move With the Full WACC Move
Because the cost of debt is scaled by (1 − tax rate) and further weighted by the debt share of capital structure, WACC rarely rises exactly one-for-one with the risk-free rate, even though the cost of equity does. A common analytical mistake is assuming a 2 percentage point Treasury yield move produces an identical 2 percentage point WACC move — the actual change depends on the company's specific capital structure, tax rate, and credit spread, and is usually somewhat smaller than the risk-free-rate move itself, as the worked example's 1.85 percentage point WACC increase illustrates.
Ignoring That Corporate Credit Spreads Move Independently of Treasury Yields
This guide's worked example holds the 2 percentage point credit spread constant to isolate the Treasury-yield channel, but spreads widen and narrow on their own based on the market's assessment of default risk, which often moves in the opposite direction from Treasury yields during stress — Treasury yields can fall on a flight to safety at the very moment credit spreads widen on rising default fear, producing a smaller or even negative net move in a specific company's cost of debt. Tracking the company's actual bond yield or CDS spread, not just the Treasury base rate, is necessary for an accurate cost-of-debt estimate.
Treating the Hurdle-Rate Effect as Uniform Across All Companies
A higher WACC does not slow every company's investment appetite equally. Highly levered companies with more of their capital structure weighted toward debt feel the compounding cost-of-debt effect more; unlevered, cash-rich companies funding growth internally are comparatively insulated from the financing-cost channel, though they still face a higher opportunity cost of capital through CAPM. For a company-level view of whether a given return actually clears its cost of capital, see Return on Invested Capital, which compares a company's realized ROIC against a cost-of-capital range rather than a single point estimate.
Frequently Asked Questions
What Is CAPM and How Does the Risk-Free Rate Set the Cost of Equity?
The Capital Asset Pricing Model (CAPM) estimates a company's cost of equity as the risk-free rate plus beta multiplied by the equity risk premium. The risk-free rate — proxied by the 10-year Treasury yield — is the baseline return investors can earn with no default risk, so it sets the floor every equity investment is priced against. Holding beta and the equity risk premium constant, a 1 percentage point rise in the risk-free rate raises the cost of equity by exactly 1 percentage point, because the risk-free rate enters the CAPM formula as a direct additive term rather than a scaled one.
What Is WACC and How Does It Blend the Cost of Equity and the Cost of Debt?
The weighted average cost of capital (WACC) blends the cost of equity and the after-tax cost of debt, each weighted by its share of the company's capital structure: WACC equals the equity weight times the cost of equity, plus the debt weight times the after-tax cost of debt. WACC represents the average return a company must generate across all its financing sources — shareholders and bondholders — to avoid destroying value. Because both the cost of equity (through CAPM's risk-free rate term) and the cost of debt (through corporate bond yields that track Treasury yields) rise together in a rising-rate environment, WACC increases from both sides of the blend simultaneously, not just one.
Why Does a Higher WACC Raise the Hurdle Rate for Corporate Investment?
WACC is the discount rate a company applies to a project's or acquisition's expected future cash flows to determine whether it creates value, so WACC functions directly as the hurdle rate a project must clear. Raising the discount rate lowers the present value of every future cash flow, meaning fewer projects produce a positive net present value at the higher rate. A project that clears an 8% hurdle comfortably can fail a 10% hurdle outright, even though nothing about the project's own expected cash flows changed. This is the direct mechanical channel through which rising rates slow corporate capital expenditure, M&A activity, and growth investment industry-wide.
How Do Corporate Bond Yields Rise Alongside Treasury Yields?
A corporate bond's yield is priced as the comparable-maturity Treasury yield plus a credit spread that compensates investors for the issuer's default risk relative to the U.S. government. When Treasury yields rise, the Treasury component of every corporate bond's yield rises with it, even if the issuer's credit spread stays completely unchanged, because the corporate yield is built on top of the Treasury base rate. This means a company's actual cost of debt — what it pays to issue new bonds or roll over maturing debt — rises directly alongside the risk-free rate, compounding the WACC increase that is already coming from the cost-of-equity side through CAPM.
Does a Rising Risk-Free Rate Always Reduce a Company's Valuation?
Not automatically, but it is a consistent headwind, all else equal. A higher risk-free rate raises WACC through both the cost-of-equity and cost-of-debt legs, which lowers the present value of a company's future cash flows and raises the bar its investment projects must clear. A company can partly or fully offset this if its expected cash-flow growth accelerates for unrelated reasons — a demand shock, a new product cycle, or margin expansion — or if the rate rise is accompanied by a falling equity risk premium as investor risk appetite improves. In practice, higher-duration companies with cash flows concentrated further in the future feel the WACC increase most acutely, while companies with near-term, less-discounted cash flows are comparatively insulated.
Sources and Further Verification
- U.S. Department of the Treasury. Daily Treasury Par Yield Curve Rates — official source for the risk-free rate used as the CAPM baseline throughout this guide.
- Federal Reserve (FRED). 10-Year Treasury Constant Maturity Rate (DGS10) — the standard 10-year Treasury yield series.
- Federal Reserve (FRED). ICE BofA US Corporate Index Effective Yield — a broad corporate bond yield series useful for tracking the credit-spread-over-Treasuries relationship described in this guide.
- Damodaran, A. (NYU Stern). Implied Equity Risk Premium data — widely cited historical and implied equity risk premium series used in CAPM cost-of-equity estimates.
Educational Disclaimer
This guide is for educational purposes only. The worked example uses simplified, hypothetical figures to isolate the risk-free-rate-to-WACC mechanism and is not a forecast or a claim about any real company's cost of capital or investment decisions. Do not make investment decisions based solely on this content. Trading involves risk of loss including total loss of principal.