How Many Contracts to Trade - Sizing Spreads by Maximum Loss

Reviewed by Leon Moyer - Published October 9, 2026 - Last reviewed October 9, 2026

The number of contracts to trade on a defined-risk spread equals your dollar risk budget divided by one spread's maximum loss, rounded down. Because a vertical spread has a known worst case, you can size it exactly. What the size cannot tell you is how quickly that worst case arrives, and that depends on the spread you choose.

The Course 1 lesson Position Sizing - How Much to Risk on Each Options Trade applied this formula to a bought option, where the maximum loss is the premium. Here it is applied to spreads, where you work out the maximum loss first.

What is the maximum loss on a spread?

A vertical spread buys one option and sells another of the same type and expiration at a different strike. The bought option caps what the sold option can cost you, so the worst case is fixed when you open the trade. Two sentences cover the common cases, per share, before fees:

• For a debit spread (you pay to open), the maximum loss is the net debit you paid. The Options Industry Council's bull call spread page describes it as "the initial outlay for the position (the net debit)."
• For a credit spread (you are paid to open), the maximum loss is the distance between the strikes minus the credit you received. The OIC's bull put spread page puts the worst case at "the stock price to be below the lower strike at expiration."

Multiply the per-share figure by 100 for one spread; the sizing formula needs that dollar figure.

How do you size a spread from its maximum loss?

The formula is the one from Course 1, with the spread's maximum loss in place of the premium: contracts equal your dollar risk per trade divided by one spread's maximum loss, rounded down.

Same setup as the Risk and Reward Math module: XYZ at $50, 30% implied volatility, 30 days to expiration and a 4.5% rate. Premiums are the free profit calculator's model prices, so you can rebuild every trade there; real quotes will differ.

Notice that the credit or debit is not the number you divide by. The 50/45 put spread collects $142, but sizing it as if $142 were the risk would let you sell three of them and put $1,074 on the line. As with a single short put, size by what the trade can lose, never by what it pays.

Same risk, different trade: wide or narrow spreads?

The second row is where beginners get surprised. Nine 50/49 put spreads and one 50/45 put spread both fit the $500 budget, and both stay under it: $495 and $358. They are not the same trade.

• The narrow spreads lose everything with a small move. Nine 50/49 spreads lose their full $495 as soon as XYZ finishes below $49, a 2% drop. The single 50/45 spread is still only $58 down at $48 and reaches its $358 maximum only below $45.
• The narrow spreads also make more if XYZ holds. Their combined credit is $405, against $142 for the wide spread. That is the trade-off: a bigger payout in exchange for a worst case that is much easier to reach.
• Fees scale with contracts. Nine spreads are 18 option contracts to open and up to 18 more to close, against 2 and 2 for the wide spread. Per-contract commissions and the bid-ask spread on each leg take a bigger share of a $0.45 credit than of a $1.42 one.

The sizing formula treats a $495 risk the same however likely it is. That is not a flaw; it is why sizing comes after choosing the spread. Pick the structure that matches your view and how far you think the stock could move against you, then let the budget decide the count.

Is the margin requirement the same as the maximum loss?

For a standard vertical spread in a margin account, usually close. FINRA Rule 4210 sets the requirement on the short option at the lesser of its own uncovered requirement or the spread's maximum potential loss, with the credit applied. Brokers can require more.

Two cautions keep this from becoming a sizing shortcut:

• Size by maximum loss, not by the broker's figure. If a broker shows a smaller number, the maximum loss has not changed.
• Early assignment can need more capital for a short time. American-style equity options can be assigned before expiration. The OIC notes that early assignment usually happens when the short put is deep in the money, and that using the long put to cover it means financing a stock position for one business day. Your loss is still capped by the long put, but the account has to carry 100 shares per spread until you act.

Cash accounts and IRAs work differently. Cboe's strategy-based margin page notes that certain limited-risk spreads, such as butterflies and boxes, can be carried in a cash account when they use European-style, cash-settled index options that expire together. For other spreads, brokers set their own cash-account and IRA rules, so check yours.

What about positions that leg in, or more than two options?

The rule stays the same: find the worst case of the whole position at expiration, then size. For an iron condor (a put credit spread plus a call credit spread), only one side can finish in the money, so the maximum loss is the wider side's width minus the total credit. If a position's worst case cannot be stated as a number, the formula does not apply, and the next lesson, Sizing Covered Calls and Cash-Secured Puts, covers positions whose worst case is large.