Capital Asset Pricing Model (CAPM): Definition, Formula, and Benefits

by Madhav Agarwal

Published On June 20, 2024

In this article

Imagine predicting the return on an investment based on its risk. In the 1960s, economists William Sharpe, John Lintner, and Jan Mossin introduced a groundbreaking model that does just that: the Capital Asset Pricing Model (CAPM). This model has since become a fundamental pillar in modern finance, offering investors and financial analysts a powerful tool for evaluating the relationship between risk and expected return on investments.

CAPM posits that the expected return on investment should be proportional to its systematic risk, measured by its beta coefficient. This model builds upon Harry Markowitz's Modern Portfolio Theory, suggesting that while investors can't eliminate all risk through diversification, they can be compensated for taking on systematic risk that affects the entire market. The elegance of CAPM lies in its simplicity, expressing the expected return as a linear function of the risk-free rate, the investment's beta, and the market risk premium. Despite its theoretical limitations and empirical challenges, CAPM remains widely used in practice, serving as a benchmark for evaluating investment performance, determining the cost of equity capital for firms, and guiding asset allocation decisions in portfolio management.

What is the Capital Asset Pricing Model (CAPM)?

The Capital Asset Pricing Model (CAPM) is an equation that describes the relationship between the expected return of an investment and its risk. The model posits that the expected return on an investment is equal to the risk-free rate plus a risk premium, which is based on the beta of that investment. Beta measures an investment's volatility relative to the market as a whole.

CAPM Formula

The CAPM formula is:

Expected Return = Risk-Free Rate + β × (Market Return - Risk-Free Rate)


  • Expected Return is the return an investor anticipates from an investment

  • Risk-Free Rate is the return on a risk-free asset, typically government bonds

  • Beta measures the volatility of an asset compared to the overall market

  • Market Return is the expected return of the market as a whole

Components of the Formula

  1. Risk-Free Rate: This represents the theoretical rate of return of an investment with zero risk, usually based on government securities like Treasury bills.

  2. Beta: A measure of the volatility or systematic risk of a security or portfolio compared to the market as a whole. A beta of 1 indicates that the security's price moves with the market.

  3. Market Risk Premium: This is the difference between the expected market return and the risk-free rate, representing the additional return investors expect for taking on the risk of investing in the market.

How to Calculate CAPM: A Step-by-Step Guide

To calculate the expected return using CAPM:

  1. Identify the risk-free rate, which is usually the yield on government bonds.

  2. Determine the investment’s beta by comparing its historical returns to the market.

  3. Estimate the expected market return.

  4. Plug these values into the CAPM formula to find the expected return.

CAPM Example

Let's consider a stock with a beta of 1.2, a risk-free rate of 3%, and an expected market return of 8%:

Expected Return = 3% + 1.2 * (8% - 3%) = 9%

This means an investor would expect a 9% return on this stock based on its risk profile.

Benefits of Using CAPM in Investment Decisions

CAPM offers several advantages for investors:

  • Risk assessment: CAPM helps investors quantify and compare the risks of different investments

  • Portfolio optimization: It aids in constructing efficient portfolios that maximize return for a given level of risk.

  • Performance evaluation: CAPM provides a benchmark for evaluating the performance of investments and portfolio managers.

Assumptions of Capital Asset Pricing Model (CAPM)

While CAPM is a useful tool, it relies on several key assumptions:

  • Investors hold diversified portfolios, eliminating unsystematic risk.

  • Markets are efficient, and all investors have the same information.

  • There are no taxes or transaction costs.

  • All investors can borrow and lend at a risk-free rate.

Criticism of the Capital Asset Pricing Model (CAPM)

While CAPM is widely used, it has several limitations

  1. Simplified assumptions: CAPM relies on unrealistic assumptions about market behavior and investor actions, such as all investors having the same level of information, All investors being rational and risk-averse and the market being in perfect equilibrium

  2. Single-factor model: CAPM only considers market risk (beta) as the sole factor affecting returns. It ignores other potential factors like company size, value, or momentum that may influence asset pricing.

  3. Beta limitations: Beta is calculated using historical data, which may not accurately predict future performance. Beta can be unstable over time. For companies with limited trading history, beta may be unreliable

  4. Risk-free rate ambiguity: Determining the appropriate risk-free rate can be challenging, especially in global investments or during economic instability.

  5. Linear relationship assumption: CAPM assumes a linear relationship between risk and return, which may not always hold in real markets

  6. Neglects unsystematic risk: CAPM focuses solely on systematic (market) risk, ignoring company-specific risks that can affect individual securities

Alternative Models to CAPM

While CAPM is widely used, some alternative models address its limitations:

  • Arbitrage Pricing Theory (APT): Considers multiple factors in determining expected returns.

  • Fama-French Three-Factor Model: Adds size risk and value risk factors to the market risk factor in CAPM.

Practical Application to CAPM

CAPM is extensively used in various areas of finance:

  • Portfolio Management: Used to assess the risk-adjusted performance of portfolios. For instance, a fund manager might use CAPM to determine the expected return of different stocks in a portfolio, helping to balance high-risk and low-risk investments.

  • Corporate Finance: Helps in estimating the cost of equity for capital budgeting decisions. A CFO might use CAPM to calculate the discount rate for future cash flows, ensuring accurate valuation of investment projects.

  • Valuation: Assists in determining the required rate of return for discounted cash flow models. Financial analysts often rely on CAPM to establish the appropriate discount rate when valuing companies.

  • Risk Management: Provides a framework for understanding and quantifying market risk. Risk managers use CAPM to evaluate the potential risks associated with market fluctuations and to develop strategies to mitigate these risks.

Additional Insights from Research

Asset pricing has found a central place in financial literature. Sharpe (1964) formulated the first asset pricing model by using the work done by Markowitz (1952). According to CAPM, the expected return of the securities is based on the market factor, captured by the beta of the stock. Beta measures the sensitivity of the stock’s return to changes in market conditions. CAPM divides the risk into two components: systematic risk and unsystematic risk.

A recent study from SRCC tested the CAPM model using Indian capital market data, specifically stocks included in the NSE 500 index. The study constructed 25 portfolios based on the beta factor and found that CAPM is not capable of explaining the variations in cross-sectional returns for the Indian stock market. This conclusion aligns with previous studies by Gupta and Sehgal (1993), Ansari (2000), and Manickaraj and Lokanathan (2004). The SRCC study, which analyzed data subdivided into four sub-periods, reaffirmed that CAPM is not relevant for asset pricing in India, highlighting the model's limitations in different market contexts.

The Bottom Line

The Capital Asset Pricing Model (CAPM) remains a fundamental tool in finance for assessing the expected return on an investment given its risk. While it has its limitations and relies on several assumptions, CAPM provides a clear framework for understanding the trade-off between risk and return.

Frequently Asked Questions

What is the purpose of the Capital Asset Pricing Model (CAPM)?

CAPM helps investors determine the expected return on an investment, taking into account its risk relative to the market.

How does CAPM help in assessing investment risk?

CAPM quantifies investment risk through beta, allowing investors to compare the volatility of an asset to the market.

Why is the Risk-Free Rate important in CAPM?

The risk-free rate serves as the baseline return for a zero-risk investment, crucial for calculating the expected return in CAPM.

Can CAPM be used for all types of investments?

CAPM is generally used for stocks and other assets that can be compared to the overall market. However, its assumptions may not hold for all asset classes.

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