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Finance · Foundations

Cost of Capital

10 min read 5 practice questions
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On this page 9 sections
  1. In 30 seconds
  2. Why this matters
  3. The college version
  4. Eli explains
  5. Worked example
  6. Key takeaway
  7. Quick check
  8. Study tools
  9. Sources & references

In 30 seconds

is the price a business pays for the money it uses: the return that lenders and owners expect for letting the business use their funds. Borrowed money costs interest; owner money costs the return owners expect. A project must earn more than the cost of the money funding it, and the overall cost is a blend of all funding sources, weighted by how much of each the business uses. Riskier businesses face higher costs. It is the business's floor for ambition.

Why this matters

Every expansion, new oven, or delivery route is paid for with money that someone provided — and that someone expects to be repaid with a return. The cost of capital names that expectation and turns it into a number a business can measure plans against. Without it, a company can spend years making moves that look profitable on paper while quietly earning less than the money funding them costs. With it, managers can sort good projects from bad, owners can judge whether the business is creating value, and lenders can price risk. It is the shared ruler that keeps ambition honest.

The college version

What the cost of capital is

Cost of capital is the price of the money a business uses. CFI puts it as the minimum rate of return a business must earn before generating value — before turning a profit, it must at least generate enough income to cover the cost of the funding its operations. OpenStax's Principles of Finance frames the same idea from the other side: the costs of debt and equity capital are what those who allow the firm to use their capital expect in return for providing it. The working definition this lesson uses combines the two framings: the cost of capital is the return that providers of money require for letting a business use their funds.

Debt money and owner money

A business's money comes from two main places, and each has its own price. Debt — money borrowed from lenders — costs interest. OpenStax defines a company's as the interest rate it would have to pay to refinance its existing debt, and CFI calls it the interest rate a company pays on its existing debt. Equity — money from owners and shareholders — costs the return those owners expect. That price cannot be read off a screen: OpenStax notes it must be estimated, and CFI agrees it is the expected return on shareholders' investment. Debt and equity have their own lessons; here they are the two ingredients whose prices together make up the cost of capital.

The core rule: out-earn the money you use

The rule that makes the cost of capital matter: a project must earn more than the cost of the money funding it. CFI states it directly — any project the company invests in must be equal to or ideally greater than its cost of capital. Original example: the owners of a diner borrow $50,000 at 8% interest to expand the dining room. The expansion must bring in more than 8% per year, on top of covering its own expenses, or the diner pays more for the money than the money earns — the owners are worse off than if they had done nothing. The interest rate is not a detail to pay and forget; it is the bar the project must clear.

The weighted idea

A business rarely runs on one kind of money, so its overall cost of capital is a blend — what finance calls the cost of capital. Each funding source has its own price, and each price counts in proportion to how much of the total funding that source provides. OpenStax describes the calculation: once you know the weights in a company's capital structure and have estimated the costs of the different sources, you can calculate the weighted average cost of capital, with the weights of all sources adding up to 100% of the company's financing. Original example: a business funded half by loans at 6% and half by owner money expected to earn 14% lands around 10% overall — a weighted blend, not a simple average of the extremes. The blend is an estimate resting on assumptions, not a precise dial reading.

A hurdle for every project

The cost of capital does its real work as a hurdle. A , CFI explains, is the minimum required rate of return investors expect on an investment, and most companies use their weighted average cost of capital as the hurdle for new projects. Before a project is accepted, its expected return must be equal to or greater than the hurdle rate; anything less is not acceptable in the long run. The hurdle sits at the door of every spending decision: a production line, a store opening, a delivery route. Projects that clear it earn their keep; those that do not are rejected even when they would make some money — making some money is not enough when the money itself costs something. The judging mechanics belong to capital budgeting and net present value, sibling topics with their own lessons.

Risk and the price of money

Risk sets the price. The riskier a business looks, the more its money costs, because providers demand compensation for higher uncertainty. CFI explains the mechanism: more debt raises the risk of default, and higher default risk increases the cost of debt as new lenders demand a premium; shareholders likewise expect a premium for the added risk. OpenStax adds that changes in the overall riskiness of a firm change the price of the securities it has issued. Original example: a utility with decades of steady bills and a young robotics startup both need $1 million. The utility's money costs less, not because it is nicer, but because providers face far less uncertainty about getting their return back. More risk, higher , higher cost of capital.

The honest framing

The cost of capital is the business's floor for ambition. Every plan — every new product, market, or building — has to beat the price of the money it uses, and that price does not bend because the idea is exciting. CFI's definition carries the whole reality check: before a business can turn a profit, it must at least generate sufficient income to cover the cost of the capital it uses to fund its operations. A business that keeps funding projects earning less than their money costs can look busy while quietly shrinking in value. The cost of capital is not a formality; it is the honest question asked of every ambition: will this earn more than the money it uses costs? If not, the ambition is not ready to be funded.

Eli, the EliExplains learning guide

Eli explains

The same idea, in plain words

Explain it like I’m 10

The cost of capital is the rent a business pays on the money it uses. Every dollar a business runs on was handed over by someone — a lender or an owner — and that someone expects a payment for letting the business use it. Lenders charge interest; owners expect a return. Add up those expectations, weighted by how much of each kind of money the business uses, and you get the cost of capital. It is also the floor: any project that earns less than the cost of the money funding it makes the business poorer, even when the project looks profitable on paper.

Picture it like this

Think of the cost of capital as the rent on a delivery van. The van is the money; the rent is what the van's owner charges for letting you use it. If you earn more with the van than the rent costs, you come out ahead. If you earn less, you pay the rent out of your own pocket and end up worse off than before — even if the van was busy all week. The rent does not care how hard you worked; it is due either way. And the riskier a driver you are, the higher the rent the van owner demands.

Where the picture stops working

A van's rent is a fixed monthly number set by one owner, but a business's cost of capital is an estimate built from many providers with different expectations, and it shifts as the business and the economy change. And while you can return a van, a business cannot simply hand its funding back — the money stays invested and keeps demanding its return.

Worked example

Ridge & Pine Woodworks wants a new saw line that will cost $200,000. Half the money comes from a bank loan at 6% interest — that is the cost of the debt. The other half comes from the owners, who expect a 14% return on the money they have tied up — the cost of the equity. Weighting each source by its half-share of the funding, Ridge & Pine's cost of capital lands around 10%. The new saw line must therefore earn more than 10% per year to be worth funding. If it is expected to earn only 9%, the project fails the test: it earns less than the money funding it costs.

Key takeaway

The cost of capital is the return providers of money expect — the price of a business's funding. Every project must clear it, or the project quietly makes the business poorer.

Quick check

3 questions here, of 5 in this lesson’s practice set. Answers stay hidden until you check.

Question 1 of 3foundational

What does the cost of capital measure for a business?

Choose an answer, then check it.
Question 2 of 3intermediate

A bakery borrows $40,000 at 8% interest to install a new oven line, which is expected to earn 6% per year. Based on the core rule of this lesson, what should the bakery's owners conclude?

Choose an answer, then check it.
Question 3 of 3advanced

Alder Utilities and Fernwood Robotics each need $1 million. Alder has decades of steady, predictable bills; Fernwood is a young company in a fast-changing market. What should be expected based on the relationship between risk and the cost of capital?

Choose an answer, then check it.
Practice all 5

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Practice this lesson
Study tools & related lessonsYou’ll learn to · Common mistakes · Easily confused · Key vocabulary · Related

You’ll learn to

  • Define the cost of capital as the return that providers of money require for letting a business use their funds, using the CFI and OpenStax framings.
  • State the cost of debt (interest on borrowing) and the cost of equity (the return owners expect) in one line each.
  • Apply the core rule that a project must earn more than the cost of the money funding it, with an original example.
  • Explain the weighted idea: the overall cost of capital is a blend of all funding sources, each counted by its share of the total.
  • Describe the cost of capital as a hurdle rate that projects must clear, and connect higher risk to higher required returns.

Common mistakes

  • Treating the cost of capital as just the interest rate.

    Interest on borrowed money is only one part. The money owners provide also carries a cost — the return they expect — and it is often the larger of the two.

  • Judging a project by profit alone.

    A project can look profitable and still destroy value if it earns less than the cost of the money funding it. The comparison is always against the cost of capital, not just against zero.

  • Assuming the overall cost is a simple average of the rates.

    If a business uses mostly cheap debt and a little expensive equity, the overall cost sits closer to the debt cost. The blend weights each source by its share of the total funding.

  • Ignoring risk when pricing money.

    Money provided to a riskier business costs more, because providers demand higher returns to compensate for higher uncertainty. A startup and a utility never pay the same rate for the same reason.

Easily confused

Cost of debt vs. Cost of equity

The cost of debt is the interest a business pays on borrowed money, known up front; the cost of equity is the return owners expect, which cannot be observed directly and must be estimated.

Cost of capital vs. Hurdle rate

The cost of capital is the price of the money itself; the hurdle rate is the minimum return a project must earn, which most businesses set at or near their cost of capital.

Key vocabulary

Cost of capital
The return that the people who provide a business's money expect to receive for letting the business use it.
Cost of debt
The interest a business pays on money it borrows; the price of using lenders' money.
Cost of equity
The return that a business's owners expect to earn on the money they have invested in it.
Weighted average
A blended figure in which each item counts in proportion to its share of the total.
Hurdle rate
The minimum return a project must earn before a business will agree to fund it.
Capital
The money a business uses to operate and grow, drawn from lenders and owners.
Investor
Someone who provides money to a business and expects a return in exchange.
Required return
The return a provider of money demands before they will supply it to a business.

Sources & references

  1. Principles of Finance, Section 17.2: The Costs of Debt and Equity Capital — OpenStax, Rice University
  2. Principles of Finance, Section 17.3: Calculating the Weighted Average Cost of Capital — OpenStax, Rice University
  3. Cost of Capital (Corporate Finance Institute) — Corporate Finance Institute (CFI)
  4. Hurdle Rate (Corporate Finance Institute) — Corporate Finance Institute (CFI)

EliExplains lessons are original prose written from the open, credible references above. See Copyright & Licensing.

Researched 2026-08-21

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