Capital Allocation Line vs Capital Market Line

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

The capital allocation line and the capital market line both describe combinations of a risk-free asset and a risky portfolio. Candidates mix them up because they look identical on paper. The difference is what sits in the risky portfolio. Level I questions test whether you know when each line applies and what happens when you plot the wrong asset on the wrong line.

Key Takeaways About Capital Allocation Line vs Capital Market Line

• The CML is one specific CAL, built only with the market portfolio as the risky asset.

• The CAL applies to any investor and any risky portfolio choice, including undiversified or actively managed portfolios.

• The CML only exists under CAPM assumptions: all investors hold the market portfolio because they share the same expectations.

• The slope of both lines equals the reward-to-variability ratio (excess return divided by standard deviation), which is the Sharpe ratio.

• The CML plots only efficient portfolios. Individual securities and inefficient portfolios do not belong on it.

• Standard deviation, not beta, is the risk measure on both the CAL and the CML.

What You Need to Know for CFA Level I

• Define the capital allocation line and identify its formula components.

• Define the capital market line and explain why it requires CAPM assumptions.

• Distinguish a risky portfolio (used in any CAL) from the market portfolio (used only in the CML).

• Calculate and interpret the slope of a CAL or CML as a reward-to-variability measure.

• Identify when a line represents a CAL versus a CML in a given exam scenario.

• Recognize that beta and the security market line belong to a different framework, not the CML.

Capital Allocation Line Definition

The capital allocation line shows every possible portfolio you can build by combining a risk-free asset with one specific risky portfolio. That risky portfolio can be anything: a single stock, an actively managed fund, or a diversified basket an advisor selected. Each investor can draw a different CAL depending on which risky portfolio they choose.

Moving along the CAL means adjusting the weight between the risk-free asset and the risky portfolio. More weight in the risky portfolio increases both expected return and standard deviation. Less weight reduces both.

Capital Market Line Definition

The capital market line is what happens when the risky portfolio in a CAL becomes the market portfolio. This only works under CAPM assumptions: investors share the same expectations about returns, risk, and correlations. When every investor analyzes the same inputs the same way, they all arrive at the same optimal risky portfolio, the market portfolio.

Because everyone holds the same risky portfolio, one CML applies to all investors. Individual differences show up only in how much of the market portfolio versus the risk-free asset each investor holds, not in which risky portfolio they select.

Risky Portfolio vs Market Portfolio

This distinction drives most exam questions on this topic.

A CAL is investor-specific and flexible. The CML is a single, shared line that only exists when the underlying risky portfolio is efficient and equals the market portfolio.

Slope as Reward-to-Variability

Both lines share the same slope formula: the risk premium of the risky portfolio divided by its standard deviation.

Formula Comparison

Capital Allocation Line:

Capital Market Line:

Where:

• = expected return of the combined portfolio

• = risk-free rate

• = expected return of the chosen risky portfolio (CAL)

• = expected return of the market portfolio (CML)

• = standard deviation of the chosen risky portfolio (CAL)

• = standard deviation of the market portfolio (CML)

• = standard deviation of the combined portfolio

The fraction is the slope. It equals the Sharpe ratio of the risky portfolio (or market portfolio, for the CML). A steeper slope means more expected return per unit of total risk. This is why the term "reward-to-variability ratio" appears in the curriculum: reward is excess return, variability is standard deviation.

Worked Example: Classifying Three Portfolios and Calculating Slope

Scenario: Three CFA candidates each build a portfolio by combining a risk-free asset with a risky asset.

• Candidate A combines the risk-free asset with a single technology stock expected to return 11% with a standard deviation of 25%.

• Candidate B combines the risk-free asset with a broad-market index fund expected to return 9% with a standard deviation of 16%, and this index fund matches the true market portfolio under CAPM assumptions.

• Candidate C combines the risk-free asset with an actively managed small-cap fund expected to return 13% with a standard deviation of 30%.

Step 1: Classify each line

Candidate A's line is a CAL. A single stock is not the market portfolio.

Candidate B's line is a CML. The risky portfolio is explicitly the market portfolio.

Candidate C's line is a CAL. An actively managed small-cap fund is not the market portfolio, even if it performs well.

Step 2: Calculate the slope (reward-to-variability ratio) for each

Candidate A:

Candidate B:

Candidate C:

Only Candidate B's line is a true CML because the risky portfolio is the market portfolio. Candidates A and C hold valid CALs, but each line is specific to their own risky asset choice. Also, notice that Candidate B's slope is the highest here.

Under CAPM, the market portfolio's Sharpe ratio should be the highest achievable, since no combination of risky assets should beat the market on a risk-adjusted basis when everyone shares the same expectations.

Common Exam Traps

Treating every CAL as the CML

A line combining the risk-free asset with any risky portfolio is a CAL. It only becomes the CML if that risky portfolio is specifically the market portfolio.

Using beta on the CML

The CML uses standard deviation (total risk) on its x-axis. Beta belongs to the security market line, which measures systematic risk only.

Placing individual securities on the CML

The CML only plots efficient portfolios: combinations of the risk-free asset and the market portfolio. A single stock sits below the CML unless it happens to be perfectly efficient, which individual securities are not.

Confusing the CML with the security market line (SML)

The CML plots expected return against standard deviation for efficient portfolios only. The SML plots expected return against beta for any asset or portfolio, efficient or not. They answer different questions.

Assuming the CML applies without CAPM assumptions

If the exam question does not state or imply homogeneous expectations and a single optimal risky portfolio, defer to the CAL, not the CML.

Practice Questions

An analyst plots a line showing combinations of a risk-free asset and a diversified small-cap equity fund. The fund is not assumed to be the market portfolio. The line has a slope of 0.40.

What does this line represent, and what does the slope measure?

1. The capital market line, where 0.40 is the fund's beta

2. The capital allocation line, where 0.40 is the fund's reward-to-variability ratio

3. The security market line, where 0.40 is the fund's risk premium

FAQs About Capital Allocation Line vs Capital Market Line