Most accounts that blow up on options do not do it by picking bad strikes. They do it by putting too much on. Strike selection decides how often you are right; position size decides whether being wrong matters.

Cash-secured puts have a particularly blunt constraint, and it is arithmetic rather than judgement: each one needs the full strike value in cash.

The arithmetic that runs the strategy

A $50 stock needs about $4,750 per contract at a 5% out-of-the-money strike. A $400 stock needs about $38,000. That single fact quietly determines which underlyings a given account can trade at all.

It is also why small accounts gravitate toward lower-priced stocks and ETFs — and why credit spreads exist, since they require the width rather than the strike.

Affordable and sensible are different numbers

The widget shows both, and the gap between them is the lesson.

Five contracts is what the balance permits. It is also a 95% bet on one company, dressed up as five separate trades. If that stock gaps 30% on an earnings miss, the account takes a $14,000 hit — and there is no diversification anywhere to soften it.

What buying power actually measures

Buying power is your broker's number for what you can still commit, and it is not your cash balance. Selling a put reduces it by the collateral required, and that reduction changes as the position moves against you.

In a margin account the reduction is smaller than the full strike value — which is exactly where the danger sits. The broker will happily let you sell more puts than you have cash to honour, and the payoff diagram looks identical right up until assignment arrives with a margin call attached.

If the collateral is not there, it is not a cash-secured put. It is a leveraged short put with a reassuring name. See cash versus margin.

Sizing rules worth actually using

Cap capital per underlying. Ten to twenty percent of the account is a common range. This is the single most protective rule available, and the widget applies it directly.

Keep a cash reserve. Twenty to thirty percent uncommitted. It funds assignment, allows rolling, and lets you act when a genuinely good setup appears rather than watching it.

Size on the worst case, not the premium. The question is never “how much will I collect”. It is “if this stock halves, what does that do to me”.

Count correlated positions as one. Five short puts on five semiconductor names is one position with five tickets — see correlation risk.

The honest position on small accounts

A $5,000 account cannot run diversified cash-secured puts. One contract on a $50 stock is $4,750 — the entire account on one company.

The realistic options are: trade defined-risk spreads, which need the width rather than the strike; trade low-priced ETFs; or keep building the account first. What does not work is running the strategy at five times the sensible size and hoping the tail stays away, which is the path most small accounts take.

What can go wrong

Sizing by contract count. Meaningless across different stock prices.

Using full buying power. Leaves nothing for assignment or adjustment, exactly when you need it.

Treating margin collateral as the real requirement. The obligation is the full strike value regardless of what the broker holds.

Adding contracts after a winning streak. The streak was structural. See probability and expected value.