What is Weighted Average Cost of Capital (WACC)?

Every dollar you use to build your business comes with a price tag.

It does not matter if the money comes from a bank loan or a venture capital investor. You have to pay for the privilege of using that capital. Weighted Average Cost of Capital, or WACC, is a calculation that tells you exactly how much that capital costs on average.

It looks at all the different ways you are funded. This usually includes debt and equity. It then weights them based on how much of each you use.

The result is a percentage. This percentage represents the minimum return you need to earn on your existing assets to satisfy your lenders and investors. If your business grows at a rate lower than your WACC, you are technically destroying value rather than creating it.

To understand the calculation, you have to look at the two main categories of capital.

First is the cost of debt. This is generally easier to figure out. It is the interest rate you pay on loans or lines of credit. Since interest expenses are often tax-deductible, the effective cost of debt is usually lower than the sticker price.

Second is the cost of equity. This is harder to pin down for a private startup. It represents the return your shareholders expect for the risk they are taking. Because startups are risky, investors expect a high return. This makes equity a very expensive form of capital.

WACC takes these two costs and weights them proportionately. If your company is funded 90% by equity and 10% by debt, your WACC will be much closer to the high cost of equity.

It is helpful to compare WACC against your Return on Investment (ROI).

Think of WACC as the hurdle rate. It is the bar you must jump over.

If you are considering a new product line or a geographic expansion, you calculate the projected ROI. If that ROI is 15% and your WACC is 10%, the project is likely a good idea. You are creating 5% of value above the cost of the money you used.

However, if the project ROI is 8% and your WACC is 10%, you should not move forward. You would be spending more to finance the project than the project returns to the business.

For early-stage companies, WACC is often quite high.

You likely do not have access to cheap bank loans yet. You rely heavily on equity from angels or VCs who demand high returns to offset the risk of failure.

This high WACC forces discipline. It means you can only pursue opportunities with massive potential upside. Modest returns are not enough when your cost of capital is hovering around 20% or 30%.

Calculating WACC for a private company involves assumptions. We do not always know the exact cost of equity without a public market to tell us.

As you look at your own funding, ask yourself these questions.

Are you accurately estimating the risk premium your investors demand? Are you over-relying on expensive equity when cheaper financing options might exist? How does your current burn rate impact your future cost of capital?

Understanding WACC moves you away from guessing and toward making financial decisions based on the true cost of fueling your business.