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Vertical Spread Strike Selection

For educational purposes only; not investment advice.

Direct answer

Section titled “Direct answer”

Choose a vertical spread’s strikes by working backward from a testable price target and deadline, not by selecting whichever contracts look cheap. For a debit spread, the long strike determines where meaningful directional exposure begins; the short strike marks the price beyond which additional expiration value is surrendered. Then reject any candidate whose executable net debit, maximum loss, target-scenario return, liquidity, or assignment exposure does not fit the plan.

There is no universally correct Delta or width. An in-the-money long leg generally costs more and behaves more like the underlying; an out-of-the-money leg costs less but requires a larger, faster move. A short strike near the defensible target is a useful starting point, not an automatic rule.

Selection framework

Section titled “Selection framework”

A Bull Call spread buys a lower-strike Call and sells a higher-strike Call with the same expiration. A Bear Put spread buys a higher-strike Put and sells a lower-strike Put. For a debit spread with width W and net debit D, quoted per share:

maximum loss = D × multiplier × quantity

maximum profit = (W − D) × multiplier × quantity

At expiration, a Bull Call breakeven is long Call strike + D; a Bear Put breakeven is long Put strike − D. These are expiration identities, not prices at which the position must be profitable before expiration. Time value, IV, skew, dividends, rates, and Bid/Ask still affect the mark.

Use this order:

  1. State the expected direction, target range, realization date, and invalidation condition.
  2. Choose an expiration after that date with deliberate time buffer; more time also means a different premium and Vega exposure.
  3. Compare several long strikes using intrinsic value, extrinsic value, Delta, liquidity, and value under the target scenario.
  4. Test short strikes near and beyond the target. Wider is worthwhile only when the extra retained payoff justifies the extra debit.
  5. Price the spread as one complex order using executable net Bid/Ask, not two optimistic leg midpoints.
  6. Reprice at the target, at invalidation, after elapsed time, and after plausible IV changes.

Bull Call example

Section titled “Bull Call example”

Assume stock at $100. Buy the 100 Call for $6.00 and sell the 110 Call for $2.00, same expiration. Net debit is $4.00, width is $10, and a standard equity-option multiplier is 100:

maximum loss = $4 × 100 = $400

maximum profit = ($10 − $4) × 100 = $600

expiration breakeven = $100 + $4 = $104

At expiration, a stock price of $108 makes the spread worth $8, for a $400 profit before fees; at or above $110, value is capped at $10, for the $600 maximum profit. If the actual target is only $105, selling the 110 Call may leave too much paid-for width unused. If the thesis targets $112, selling the 105 Call caps too early.

Do not infer a 40% market probability from $400 ÷ ($400 + $600). That ratio is only the break-even win rate in a toy model where every outcome equals maximum profit or maximum loss. Real trades have a distribution of exits, slippage, and partial outcomes.

For a Bear Put analogue, buying an 80 Put, selling a 70 Put, and paying $3.50 gives $350 maximum loss, $650 maximum profit, and a $76.50 expiration breakeven. At $74 on expiration, spread value is $6 and profit is $250; below $70, value remains capped at $10.

Risks and execution controls

Section titled “Risks and execution controls”
  • The underlying can move in the expected direction but not far enough, soon enough, or before IV falls.
  • A narrow spread may have low absolute debit yet poor economics after Bid/Ask, fees, and additional contracts.
  • A wide spread can charge for payoff beyond the realistic target; a close short strike can surrender useful upside or downside.
  • Displayed midpoint combinations may not be executable. Enter and exit with a net limit on a complex order where available.
  • American-style short legs can be assigned early, especially around dividends or when little extrinsic value remains. Exercise and assignment can create stock, funding, and margin obligations.
  • Expiration can create pin and contrary-exercise risk. Closing before expiration can reduce, but not eliminate, operational risk.
  • Size from the full maximum loss. Limited loss per spread does not make an oversized quantity safe, and correlated spreads can be one concentrated bet.
  • Define profit, time, and thesis-invalidation exits before entry. Closing legs separately temporarily changes the risk profile.

Common misconceptions

Section titled “Common misconceptions”
  • “The widest spread is best.” Extra width costs money and may lie beyond the target.
  • “The narrowest spread is safest.” Friction can consume more of its payoff, and traders may compensate with excessive quantity.
  • “A fixed Delta selects the correct long strike.” Delta is an input, not a substitute for target, time, price, and liquidity.
  • “Maximum profit is expected profit.” Maximum profit usually requires a particular expiration settlement; evaluate the target scenario instead.
  • “Breakeven applies immediately.” The formula describes expiration payoff, while pre-expiration value includes time and IV.
  • “A debit spread has no assignment risk.” Its short American-style leg can be assigned before expiration.
  • “Limited risk means no exit rule is needed.” Waiting for full loss can waste the entire risk budget after the thesis has failed.
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Authoritative sources

Section titled “Authoritative sources”