Position sizing cash-secured puts: survive the red weeks first

Every put seller eventually meets the week where the whole screen turns red. Five positions drop together, every short put goes in the money at once, and the account that felt comfortably diversified suddenly behaves like one big trade. What separates traders who sail through that week from those who never recover is rarely stock picking or strike selection — it is position sizing, decided long before the selloff. This tip lays out a sizing framework for cash-secured puts (CSPs): a hard cap per underlying, a sector limit, a real cash buffer, and measuring risk in delta-adjusted dollars instead of contract counts — finished with a fully worked $50,000 example.

Sizing is the skill that keeps you in the game

Selling puts has a lopsided payoff profile: many small wins, occasional deep drawdowns. The premium on a 35-DTE, 0.30-delta put might be $0.90 per share — about 2.0% of the collateral, roughly 21% annualized if the trade could be repeated all year. That income stream only compounds if you are still solvent, and emotionally intact, after the bad weeks. Post-mortems of blown-up premium-selling accounts almost always show the same cause: not a bad ticker, but a position so large that a normal 15–20% drawdown in one name became an account-level event. Strike selection decides how often you get assigned; sizing decides whether assignment is a routine wheel event or a crisis.

Rule 1 — Cap collateral per underlying

A cash-secured put reserves the full exercise value — the strike × 100 per contract — until the position is closed, expires or is assigned. That collateral is your true position size, so cap it per underlying: a common range is 5–10% of the portfolio for any single stock. On a $50,000 account, a 10% cap means at most $5,000 reserved per name — one $50-strike contract, or two $25 strikes. Broadly diversified index ETFs pool single-company risk, so many traders allow them a higher cap, around 12–15%. And if a single contract already blows through your cap, the underlying is simply too expensive for the account size — skip it rather than stretch the rule.

Rule 2 — Cap sectors, not just tickers

Five different semiconductor tickers are not five positions; they are one trade wearing five hats. In stress weeks, correlations inside a sector move toward 1: the same macro headline pushes every one of your short puts into the money simultaneously. A practical guard is to cap total CSP collateral per sector at roughly 25% of the portfolio, counting a sector ETF toward its own sector and a broad-market ETF as its own diversified bucket. The goal is that no single earnings theme, commodity move or rate decision can hit the majority of your collateral at once.

Rule 3 — Keep a real cash buffer

In a cash account the collateral for each put is already reserved, so assignment itself does not require new money. What the red week takes away is flexibility: after one or two assignments you are holding shares, premiums on new puts are rich, and the best strikes of the year are on sale — but only for traders who kept dry powder. Holding 20–30% of the account in unreserved cash means you can roll a tested put for a small debit when it makes sense, take assignment calmly and pivot to covered calls, and still open one or two new CSPs at depressed strikes instead of watching from the sidelines.

Measure delta-adjusted exposure, not contract count

Three contracts on a $20 stock and three on a $90 stock are wildly different risks, and two 0.15-delta puts are not the same as two 0.40-delta puts. A cleaner day-to-day gauge is delta-adjusted exposure: delta × strike × 100 per contract. A 0.30-delta put on a $45 strike behaves today like owning about 30 shares — roughly $1,350 of directional exposure — even though $4,500 is reserved. Delta moves, so this number grows as a position goes against you, which is exactly why it is a better early-warning signal than a static contract count.

A worked $50,000 example

Read the totals, not just the rows. The book commits $36,900 of collateral — 73.8% of the account — leaving a $13,100 buffer at 26.2%, inside the 20–30% target. No single stock exceeds 10%; the two technology names together reach 18.2%, under the 25% sector cap; the ETF uses its wider 15% allowance. Yet the delta-adjusted total is only $8,738 — about 17.5% of the account behaves like stock today. If every position were assigned in a crash, the account would own eight diversified positions bought at strikes it pre-approved, with $13,100 in cash left to sell covered calls, add selectively, or simply wait.

1. Collateral for this name (strike × 100 × contracts) stays at or under 10% of the portfolio — up to 15% only for a broadly diversified ETF.
2. Total collateral in this sector, including the new trade, stays under 25%.
3. After reserving the collateral, unreserved cash still covers at least 20% of the account.
4. Total delta-adjusted exposure stays where you want your effective stock exposure to be.
5. You could take assignment on every open put tomorrow, in a cash account, without touching margin — and still follow your plan.