Every cushion figure in the calculator is computed on a blended beta: each holding weighted by its share of the book, then the market fall that would exhaust your margin divided by the result. A book that falls faster than the index runs out of room sooner, at the same dollar exposure. So the beta applied to your holdings is not a footnote, it is an input to the number that says whether a position survives.
These are the figures the tool applies, measured 2026-08-29 as cov(r, rSPY) / var(rSPY) over three years of daily returns:
| Symbol | Beta | Name |
|---|---|---|
| QQQ | 1.266 | Invesco NASDAQ-100 |
| QQQM | 1.256 | Invesco NASDAQ-100 (M) |
| IWM | 1.117 | iShares Russell 2000 |
| VTI | 1.006 | Vanguard Total Stock Market |
| SPYM | 1.000 | State Street SPDR Portfolio S&P 500 |
| SPY | 1.000 | SPDR S&P 500 |
| VOO | 1.000 | Vanguard S&P 500 |
| IVV | 1.000 | iShares Core S&P 500 |
| CASH | 0.000 | cash / money market |
They are measured rather than looked up because published betas disagree. The figure depends on the window, the return frequency and the benchmark, and a vendor rarely states which it used. A number quoted to two decimals with no method behind it is not more precise than one you compute yourself, it is only quieter about its assumptions.
The gap between a rounded beta and a measured one is not academic. On a portfolio that is 58% QQQM, rounding the NASDAQ holdings to 1.15 gives a blended 0.963, while the measured figures give 1.017. That is the difference between a book that falls slower than the index and one that falls slightly faster, and it moves the market fall that would liquidate you by three points.
There is a second table, measured differently, and the difference is the point. The one above covers the funds most readers hold and is measured on daily returns. Behind it sits a much longer table covering the S&P 500 and the Nasdaq-100 names outside it, measured on weekly returns.
Daily returns attenuate: two funds tracking the same index measured 0.974 and 0.979 daily against 1.000 weekly, while holding the same thing. Beta scales a book for its cushion, so an understated one overstates the room, and that is the direction it is wrong in. A beta is not comparable across methods, which is the first thing to ask of any published one.
A name whose beta cannot be measured well is dropped rather than guessed, and it then shows as an assumed 1.00 on its own row, with the blended figure saying what share of the book is on that footing. That fallback overstates exposure for a low-beta stock and therefore understates the cushion, which is the safe direction. It is only dangerous for a high-beta stock, and those are the names that survive the filter.
Why they go stale
Beta is not stable, and it does not drift in a convenient direction. It rises in exactly the selloffs the cushion exists to survive, as correlations across equities converge and the things that usually diversify a book stop doing so. A table measured in a calm year therefore understates the risk it is used to compute, at the moment that understatement costs the most.
The build warns when these figures are more than six months old, which is a reminder rather than a fix. Treat every cushion here as computed on a beta that was true in an ordinary market, and assume the real one is higher when it matters.
What the blend leaves out
Cash and money market funds are held at beta 0 and stay in the blend. That is not a gap, it is the correct answer: cash does not fall with the index, so a book holding it genuinely falls less, and the blended figure should say so.
Option contracts are excluded from the blend entirely. A contract is a liability at market value rather than market exposure, and this tool models no option delta, so it has no beta to contribute. Carrying one at zero would not be neutral. It would pull the blended figure toward 1.00 and make a concentrated book read as closer to the index than it is, which is an error in the direction that flatters the account.
Contracts still count toward equity, because equity is what the account is worth and that is what the contract count is sized from. They are absent from the beta blend and from nothing else. The consequence worth understanding: the cushions treat a contract as a fixed value rather than modelling how it behaves in a fall, so a book whose contracts are large relative to its shares is described less well by every figure here.