How CAPM turns risk into a required return
CAPM builds a required return in two layers. The first is therisk-free rate — what you could earn with no risk, typically proxied by a government bond yield. The second is a risk premium: the extra return for bearing market risk, equal to the equity risk premium (Rm − Rf) scaled by the asset’s beta. An asset that moves exactly with the market (β = 1) earns the full premium; a defensive asset (β < 1) earns less, and an amplifying one (β > 1) earns more. Adding the two layers gives the expected return investors should demand for holding that specific asset.
The CAPM formula
E(R) = Rf + β · ( Rm − Rf )
where Rf = the risk-free rate, β = beta, the asset’s sensitivity to market moves, and Rm = the expected market return. The term (Rm − Rf) is the equity risk premium, the reward for holding the market portfolio over a risk-free asset, which beta then scales up or down for the individual asset.
What makes this calculator different
- It breaks the return into its parts. Rather than just printing a single number, it separates the risk-free base from the risk premium contribution (β times the equity risk premium), so you can see exactly where the required return comes from.
- It explains beta in plain English. A beta of 1 moves with the market, above 1 is more volatile, below 1 is defensive, and a negative beta moves opposite the market — the calculator frames the number, not just reports it.
- It connects to the cost of equity used elsewhere. The required return CAPM produces is the cost of equity that flows into discounted cash flow models and theWACC calculator, so this is the natural first step in valuing a company.
Frequently asked questions
What is the Capital Asset Pricing Model (CAPM)?+
CAPM is the standard way to estimate the return an investor should require from an asset given the market risk it carries. Its formula is E(R) = Rf + β(Rm − Rf): the expected return equals the risk-free rate plus beta times the equity risk premium. The idea is that investors should only be rewarded for risk they cannot diversify away — systematic, market-wide risk captured by beta — not for company-specific risk that a diversified portfolio removes. The output is most often used as the cost of equity, the return shareholders demand for bearing that risk.
What is beta?+
Beta measures how sensitive an asset’s returns are to moves in the overall market. A beta of 1 means the asset tends to move in line with the market; greater than 1 means it amplifies market moves and is more volatile; less than 1 means it is defensive and dampens them. A negative beta is rare and implies the asset tends to move opposite the market, which can make it a useful hedge. Beta is the only asset-specific input in CAPM, so it does all the work of distinguishing one stock’s required return from another’s.
What is the equity risk premium?+
The equity risk premium is the term (Rm − Rf): the extra return investors expect from holding the market portfolio instead of a risk-free asset like a government bond. It is the reward for taking on equity-market risk in general. In CAPM, this premium is scaled by beta — an asset with a beta of 1 earns the full premium, while a beta of 0.5 earns half of it. Estimates of the premium vary, but it is typically a few percentage points and is one of the most consequential assumptions in any CAPM calculation.
What is CAPM used for?+
CAPM’s most common use is estimating the cost of equity — the return a company must offer shareholders — which then feeds discounted cash flow (DCF) valuations and the weighted average cost of capital (WACC). Analysts also use it to set the discount rate for valuing projects and to judge whether an asset is attractive by comparing its expected return against the return CAPM says it should require. If expected return exceeds the CAPM-required return, the asset may be undervalued; if it falls short, it may be overpriced for its risk.
What are CAPM’s limitations?+
CAPM rests on simplifying assumptions that rarely hold perfectly. It treats market risk as a single factor, so it ignores other drivers of return such as size, value, or momentum that multi-factor models capture. It assumes beta is stable, yet beta is estimated from past data and is backward-looking, so it can shift over time. It also assumes efficient markets, frictionless trading, and that investors can borrow and lend at the risk-free rate. Because of these constraints, CAPM is best treated as an educational benchmark and a starting point rather than a precise prediction.
Disclaimer: This calculator is foreducation and illustration only. CAPM is a model built on simplifying assumptions (a single market-risk factor, stable beta, and efficient markets), and beta is estimated from historical data, so its output is an estimate rather than a guarantee of future returns. Nothing here is investment, tax, or financial advice.