Position sizing for options

The sizing rules from the risk management course apply to options, but the inputs are different. A stock position has one number for risk: entry minus stop, times shares. An option position has a maximum loss that may be the whole premium, a probable loss that is smaller, a notional exposure that is much larger, and Greeks that change all of it daily. This lesson gives you a way to size that survives contact with all four.

Rule 1: size long options on the full premium

For a long call, put or debit spread, the maximum loss is the premium and it is realised routinely. So the premium is the risk, and the 1% (or whatever your plan says) applies to it directly.

Account $20,000, risk per trade 1% = $200.

Two things fall out. First, a small account cannot buy the ATM option on a $50 stock at 1% risk; that is information, not a problem to work around by risking 2.5%. Second, the cheap OTM call "allows" two contracts, which is precisely how people end up with a portfolio of lottery tickets. Sizing by premium is correct; choosing the strike to fit the size is backwards.

Some traders use a stop on the option (say −50%) and size on that instead: $200 risk at −50% allows $400 of premium. That works only if you actually take the stop, and long options gap through stops on overnight moves and IV changes. Sizing on the full premium is the conservative default.

Rule 2: size short options on the realistic loss, not the credit

For a credit spread, the maximum loss is the width minus the credit, and while the probability of the full loss is low, the probability of a large partial loss is not. Size on max loss, or on the management stop if you are disciplined about it.

Same $20,000 account, 1% risk, bull put spread 45/40 for $0.45 (max loss $455):

• Sizing on max loss: $200 ÷ $455 = 0 contracts. Too big for this account at 1%.
• Sizing on a 2× credit stop ($90 loss): $200 ÷ $90 = 2 contracts. Max loss if the stop is gapped through: $910, or 4.6% of the account.

The second approach is what most credit-spread traders do, and the last line is the number they need to have looked at. An overnight gap through the short strike is not rare on individual stocks.

For naked short options (uncovered puts or calls), sizing on the credit is meaningless. Size on the notional (strike × 100) as if it were a stock position, apply your position cap from the risk plan, and understand that the stop is unlikely to fill where you place it on a gap.

Rule 3: net delta as a portfolio check

Position-by-position sizing misses correlation. Ten separate 1% option positions that are all bullish on stocks are one 10% bet on the market. From Module 3, net delta in share-equivalents, times the stock price, is the dollar exposure. Sum it across the book:

A $3,510 net long exposure on a $20,000 account is 17.5% long the market, which is fine, but it is a number you should know. A 5% market drop costs roughly $175 across the book before gamma. Track it weekly at least.

Key idea: Size long options and debit spreads on the full premium. Size credit spreads on the max loss or a disciplined stop, and check what a gap does to the stop. Sum dollar delta across the book, because option positions are correlated like the stocks under them.

Rule 4: cap the number of open positions

Options positions require more attention than stock positions: expirations, ex-dividend dates, short-strike tests, rolls. A trader who can manage five stock positions can manage perhaps three option positions to the same standard. More positions than you can watch is a risk that does not appear in any sizing formula.

Rule 5: separate event trades

A long option into earnings has a realistic chance of −100% in one night. Size it at half your normal risk or less, and treat it as a separate bucket from directional swing trades. If your plan allows 1% per trade, a common split is 0.5% for event trades, 1% for swings, and a total event exposure across all names of no more than 2% at any one time.

A worked sizing sequence

Account $20,000, plan: 1% per swing trade, 0.5% per event trade, 25% cap on any single stock notional, total portfolio dollar delta within ±30% of account.

You want to buy a 60-day $50 call on XYZ at $3.30 as a swing trade.

1. Risk budget: $200. Premium $330. Zero contracts. Consider the 50/55 spread at $1.70: one contract, $170 risk. Fits.
2. Notional check: the spread controls 100 shares of a $50 stock, $5,000 notional, 25% of the account. At the cap; fine.
3. Delta check: spread delta 0.28 × 100 × $50 = $1,400 dollar delta. Current book net is +$3,510; new total +$4,910 = 24.6% of account. Under 30%; fine.
4. Position count: three open positions, this is the fourth. At your limit; either close something or skip.

Four steps, each a number, and the answer came out as "one spread contract, if you close something else". That is what sizing is supposed to produce.

Try it: Take your current or paper option book. Compute for each position: risk as sized (premium or stop), max loss, notional, and dollar delta. Sum the last two. Compare each total to your plan's caps. If you have no plan with caps, write one using the risk management course template before the next trade.

Recap

• Long options and debit spreads: risk = full premium; size the count from that and let the strike follow.
• Credit spreads: size on max loss or a disciplined stop, and check what a gap through the short strike does.
• Naked short options: size on notional (strike × 100) as a stock position, with your position cap.
• Sum dollar delta across the book; correlated option positions are one bet on the market.
• Cap open position count, and run event trades in a smaller, separate bucket.