Optimal and Target Capital Structures

Updated for the 2026-2027 CFA® Level I curriculum.

A company's capital structure is the mix of debt and equity it uses to fund operations. The optimal capital structure is the mix that minimizes the company's weighted average cost of capital (WACC) and maximizes its value. CFA Level I candidates need to describe this concept, distinguish it from a target capital structure, and explain why the two are not always the same number. This note builds on the Modigliani-Miller propositions and connects directly to WACC.

Key Takeaways

• Optimal capital structure minimizes WACC and maximizes company value.

• Target capital structure is the practical debt-equity range a company actually manages toward.

• The optimal structure is theoretical. Analysts estimate it, they do not observe it directly from one financial ratio.

• Companies rarely sit exactly at their target. They move toward it gradually as financing needs arise.

• A falling WACC as debt increases suggests the company is moving closer to its optimal mix, up to a point.

• Beyond that point, added financial risk and distress costs push WACC back up.

• Mixing up "optimal" and "target" is a common candidate error on exam questions.

What You Need to Know for CFA Level I

• Define optimal capital structure as the mix that minimizes WACC and maximizes value.

• Define target capital structure as the practical financing range a company manages toward.

• Explain the inverse relationship between WACC and company value at the optimal mix.

• Recognize that market conditions and financing constraints can keep a company away from its exact target at any point in time.

• Understand that a target capital structure reflects the optimal structure, adjusted for real-world practicality.

• Avoid confusing this concept with the Modigliani-Miller propositions, which explain the theory behind why capital structure can affect value under certain assumptions.

What Is an Optimal Capital Structure?

The optimal capital structure is the combination of debt and equity that minimizes a company's WACC. Since a lower WACC generally supports a higher company value, the optimal structure also represents the mix that maximizes firm value, all else equal.

Debt is usually cheaper than equity because interest payments are tax deductible and debt holders take less risk than equity holders. Adding debt to a capital structure can lower WACC at first. But more debt also raises financial risk. Lenders and shareholders both demand higher returns to compensate for that risk. At some point, the cost of added financial risk outweighs the tax benefit of debt, and WACC starts rising again.

The optimal structure sits at the low point of this WACC curve. It is a theoretical concept. No company can pinpoint it with certainty, because the exact costs of debt and equity shift with market conditions, business risk, and investor expectations.

What Is a Target Capital Structure?

A target capital structure is the debt-equity mix a company's management actually aims to maintain over time. It is a practical policy, not a precise theoretical point.

Management sets a target range based on its best estimate of the optimal structure, then adjusts for real constraints. These include market conditions, credit rating goals, cash flow stability, and the need for financing flexibility. A company might target 30 to 40 percent debt, for example, rather than committing to one exact ratio.

The target gives management a working guide for financing decisions. When the company needs new capital, it chooses debt or equity based on where it currently sits relative to that target range.

Optimal vs Target Capital Structure

How Companies Move Toward a Target Capital Structure

Companies rarely rebalance their capital structure all at once. Instead, they move toward their target gradually through normal financing activity.

A company below its debt target might issue bonds instead of new shares the next time it raises capital. A company above its debt target might use retained earnings or issue equity to pay down debt. Market timing also plays a role. Management may delay a debt issuance if interest rates are unusually high, even if the target calls for more debt.

These decisions happen alongside the broader set of factors covered in the Factors Affecting Capital Structure and WACC note, including business risk, tax rates, and lender agreements. This note focuses only on the optimal-versus-target distinction. The full list of influencing factors lives in that companion note.

Common Exam Traps

Treating optimal and target as the same thing

They are related but not identical. Optimal is theoretical. Target is the practical range management actually uses.

Assuming one ratio reveals the optimal structure

A single debt-to-equity ratio does not confirm a company sits at its optimal mix. The optimal point depends on multiple shifting inputs, including the market cost of debt and equity.

Assuming instant rebalancing

Candidates sometimes assume a company adjusts to its target immediately after a shock, like a large debt issuance. In practice, movement toward target happens over multiple financing decisions.

Repeating factor lists instead of applying the concept

This note is about the optimal-versus-target distinction, not a full list of capital structure determinants. Save that detail for the dedicated factors note.

Practice Question

A company has a target capital structure of 40 percent debt and 60 percent equity. Its current structure is 25 percent debt and 75 percent equity. The company needs to raise new capital for a plant expansion.

Which financing choice would move the company closer to its target capital structure?

1. Issue new common shares to fund the expansion

2. Issue new long-term debt to fund the expansion

3. Use retained earnings to fund the expansion without new financing

FAQs About Optimal and Target Capital Structures