Pronounced as though it were spelled "capm", this model was originally developed in 1952 by Harry Markowitz and finetuned over a decade later by others, including William Sharpe. The capital asset pricing model (CAPM) describes the relationship between risk and expected return, and it serves as a model for the pricing of risky securities.
CAPM says that the expected return of a security or a portfolio equals the rate on a riskfree security plus a risk premium. If this expected return does not meet or beat our required return, the investment should not be undertaken.
The commonly used formula to describe the CAPM relationship is as follows:
Required (or expected) Return = RF Rate + (Market Return  RF Rate)*Beta 
For example, let's say that the current risk freerate is 5%, and the S&P 500 is expected to return to 12% next year. You are interested in determining the return that Joe's Oyster Bar Inc (JOB) will have next year. You have determined that its beta value is 1.9. The overall stock market has a beta of 1.0, so JOB's beta of 1.9 tells us that it carries more risk than the overall market; this extra risk means that we should expect a higher potential return than the 12% of the S&P 500. We can calculate this as the following:
Required (or expected) Return =  5% + (12%  5%)*1.9 
Required (or expected) Return =  18.3% 
What CAPM tells us is that Joe's Oyster Bar has a required rate of return of 18.3%. So, if you invest in JOB, you should be getting at least 18.3% return on your investment. If you don't think that JOB will produce those kinds of returns for you, then you should consider investing in a different company.
It is important to remember that highbeta shares usually give the highest returns. Over a long period of time, however, high beta shares are the worst performers during market declines (bear markets). While you might receive high returns from high beta shares, there is no guarantee that the CAPM return is realized.
Financial Concepts: Conclusion
Related Articles

Investing
Capital Asset Pricing Model  CAPM
CAPM is a model that describes the relationship between risk and expected return. 
Investing
The Capital Asset Pricing Model: an Overview
CAPM helps you determine what return you deserve for putting your money at risk. 
Investing
The Capital Asset Pricing (CAPM) Model: Pros and Cons
CAPM, while criticized for its unrealistic assumptions, provides a more useful outcome than either the DDM or WACC in many situations. 
Investing
Taking Shots At CAPM
Find out why many investors think the capital asset pricing model is full of holes. 
Tech
CAPM vs. Arbitrage Pricing Theory: How They Differ
Both project the expected rate of return given the level of risk assumed, but they consider different variables. 
Investing
How AQR Places Bets Against Beta
Learn how the bet against beta strategy is used by a large hedge fund to profit from a pricing anomaly in the stock market caused by high stock prices. 
Investing
Reduce Your Risk With ICAPM
Avoid unnecesary risks involved in CAPM calculations by also incorporating ICAPM into the mix. 
Investing
Introduction To International CAPM
ICAPM is one of several models used to determine the required return on an asset, discover its limitations and how to use it.