Portfolio Beta Calculator
Enter each holding’s market value and its beta, and this works out the weighted-average beta of the whole book: how much the portfolio should move for a given move in the index, based on the numbers typed in. Free, no signup.
Where the beta figures come from
This tool does not fetch beta. Beta is typed in per holding, read off a brokerage position page or a data site such as a broker’s research tab or a financial data provider. Different sources compute beta over different lookback windows and against different benchmarks, so the same ticker can show a different beta in two places. Cash is always treated as beta 0. Up to 30 holdings.
Your holdings
Market value is what that position is worth today. Beta can be negative, for something like an inverse fund that moves opposite the index.
Portfolio beta: 0.91
Portfolio beta
0.91
The weighted average of every row’s beta, cash included at 0.
Cash weight
14.29%
$10,000.00 of $70,000.00 total, diluting the beta above toward zero.
From the top 3 holdings
100%
Share of the 0.91 portfolio beta coming from VOO, QQQ.
Where each holding contributes
Contribution is a holding’s weight times its beta. The contributions, including cash at zero, sum to the portfolio beta above.
| Holding | Market value | Weight | Beta | Contribution |
|---|---|---|---|---|
| VOO | $40,000.00 | 57.14% | 1.00 | 0.57 |
| QQQ | $20,000.00 | 28.57% | 1.20 | 0.34 |
| Cash | $10,000.00 | 14.29% | 0.00 | 0.00 |
| Total | $70,000.00 | 100% | 0.91 |
What that beta implies
A linear approximation only: multiplying the index move by the portfolio beta above. It says nothing about a single position moving on its own news, and it does not hold in a market that moves in a way this book’s history did not capture.
| If the index moves | The portfolio implies |
|---|---|
| 1% | 0.91% |
| 5% | 4.57% |
| 10% | 9.14% |
The part a calculator cannot do
This page weights beta figures typed in by hand. The harder part is keeping the market values current across every account and knowing which few positions are actually driving that number. Helm reads the holdings in the accounts you connect, read-only, and shows exposure and concentration by position, so the weights behind a figure like this stay current without retyping them.
See your own exposureThe weighted-average shortcut
Beta is properly defined as the covariance of a holding’s returns with the index’s returns, divided by the variance of the index’s returns. Running that regression on a whole portfolio’s return series gets the same answer, to a close approximation, as taking the weighted average of each holding’s individual beta. That shortcut is what this calculator does: it never runs a regression, it only weights the beta figures typed in.
Up to 30 holdings, plus cash
Add a row for each position with its current market value and its beta. Cash and cash-equivalent balances go in the separate field at the bottom and are always treated as a beta of zero, since a dollar in a money market fund does not move with the index.
What beta misses
Beta describes co-movement with an index, not total risk. A holding with a low beta can still carry large idiosyncratic risk, the part of its price movement that has nothing to do with the market, from a product recall to a lost customer. Beta is also computed over a specific lookback window against a specific benchmark, so it can shift as that window rolls forward or if the benchmark changes, and the relationship it describes is a historical average, not a fixed multiplier that holds in every market regime, such as a sharp, correlated sell-off where most betas move toward one.
Frequently asked questions
What is portfolio beta?
Portfolio beta is the weighted average of the beta of every holding in a book, cash included at a beta of zero. It estimates how much the whole portfolio should move for a given move in a benchmark index, based on how each holding has historically moved relative to that index.
How do you calculate portfolio beta?
Multiply each holding's weight, its market value divided by the total portfolio value, by that holding's beta, then add the results across every holding. A position that is half the portfolio contributes half of its beta to the total; a position that is one-tenth contributes one-tenth of its beta.
Where does the beta for each holding come from?
This calculator does not fetch beta. It is typed in from a brokerage research page or a financial data site, and it is worth checking the benchmark and lookback window each source uses, because the same ticker can carry a different beta on two different pages.
Why does cash lower portfolio beta?
Cash does not move with the market, so it is treated as a beta of zero. Any dollar sitting in cash contributes nothing to the weighted average, which pulls the overall figure toward zero as the cash weight rises, all else equal.
Can portfolio beta be negative?
Yes, when a position with a large negative beta, such as an inverse fund, carries enough weight to outweigh the positive-beta holdings. A negative portfolio beta implies the book is expected to move opposite the index on average, though this is a historical relationship, not a guarantee.
Related reading
Not investment advice. Beta figures are the ones typed into the form; this page does not fetch or verify them against any source, and it computes a linear, historical approximation only.