Portfolio Beta Calculator
Compute the weighted beta of a multi-stock portfolio to measure its sensitivity to broad market moves. Use it when rebalancing holdings or assessing overall market risk before a trade.
About this calculator
Portfolio beta measures how much your combined holdings are expected to move relative to the overall market. A beta of 1.0 means the portfolio moves in lockstep with the market; above 1.0 signals amplified swings, while below 1.0 indicates lower volatility. The weighted portfolio beta is calculated as: β_portfolio = (w₁ × β₁) + (w₂ × β₂) + (w₃ × β₃), where each weight is the stock's percentage of the total portfolio divided by 100. This additive property means a large position in a high-beta stock can dramatically shift your overall risk profile. Investors use this metric to align their portfolio's risk level with their personal risk tolerance or to hedge against market downturns by targeting a specific beta.
How to use
Suppose your portfolio holds three stocks: Stock A is 50% of your portfolio with β = 1.4, Stock B is 30% with β = 0.8, and Stock C is 20% with β = 1.1. Plug in the values: β_portfolio = (50/100 × 1.4) + (30/100 × 0.8) + (20/100 × 1.1) = 0.70 + 0.24 + 0.22 = 1.16. A portfolio beta of 1.16 means your holdings are expected to be about 16% more volatile than the market. If the S&P 500 drops 10%, your portfolio might decline roughly 11.6%.
Frequently asked questions
What does a portfolio beta greater than 1 mean for my investments?
A portfolio beta above 1.0 means your holdings are more volatile than the benchmark market index. For example, a beta of 1.3 implies that if the market rises 10%, your portfolio might gain around 13% — but losses are amplified equally on the downside. Aggressive growth investors often accept higher beta for greater return potential, while conservative investors target beta below 1.0 for smoother ride. It is important to remember that beta measures systematic risk only and does not capture company-specific risks.
How do I reduce the beta of my existing portfolio?
You can lower portfolio beta by increasing the weight of low-beta or defensive assets such as utilities, consumer staples, or bonds. Selling high-beta growth stocks and replacing them with dividend-paying blue-chip stocks is a common rebalancing strategy. Adding inverse ETFs or put options can also reduce effective beta for a hedging period. Recalculating your portfolio beta after each trade ensures you stay within your target risk range.
Why is portfolio beta different from an individual stock's beta?
An individual stock's beta reflects its own volatility relative to the market, which can be quite extreme for small-cap or sector-specific names. Portfolio beta is the market-cap-weighted average of all constituent betas, so diversification naturally smooths out extreme individual values. A portfolio of 20 stocks with varying betas will almost always have a beta closer to 1.0 than any single holding. This diversification effect is one of the core arguments for holding a broad basket of securities rather than concentrating in a few names.