Diagonal Spread: how the position works
A calendar spread with the strikes moved apart: sell a near-dated option at one strike and buy a longer-dated one at another. It combines the time-decay harvesting of a calendar with the directional lean of a vertical, and the strike choice decides which of the two dominates. Used at wide strikes and long back-month expiries it becomes the "poor man's covered call", a stock replacement built entirely from options.
- Market view
- Directional — with a time component
- Opened for
- Debit
- Maximum profit
- No closed form, for the same reason as the calendar: the back leg survives the front expiry and must be valued by a model.
- Maximum loss
- Bounded by the net debit when the long leg is more valuable than the short at every price — which is not automatic. Verify it with the payoff curve for your specific strikes rather than assuming it.
- Breakeven
- Model-dependent. Read it off the curve on this page.
How it is built
- Sell 1 option at strike K₁ expiring at T₁
- Buy 1 option at strike K₂ expiring at T₂, with K₁ ≠ K₂ and T₂ > T₁
All figures above are quoted per share and settle at expiry. A standard equity option covers 100 shares, so multiply by 100 for a single contract.
Before expiry: the Greeks
Long vega and positive theta like a calendar, plus a directional delta from the strike offset. Because the two legs sit at different strikes on different expiries, they also sit at different points on the volatility surface, so the position is exposed to skew changes as well as to level and term structure.
When to use it
When you have a directional lean and want the short leg to fund it, or as a capital-efficient stock replacement: a deep in-the-money long-dated call with a near-dated out-of-the-money call sold against it behaves much like a covered call for a fraction of the capital.
What goes wrong
- The loss is only bounded if the long leg dominates at every price. A poorly chosen pair can leave a gap where the short leg outruns the long one.
- Assignment on the short leg against a longer-dated long leg is not a closed position and can require capital at short notice.
- It carries level, term-structure and skew exposure at once, which makes attributing a loss harder than in any other structure here.
A worked example
SPY at 580. Sell the 595 call expiring in 21 days for 3.90, buy the 585 call expiring in 60 days for 12.60.
- Net debit paid
- $8.70 per share — $870
- Directional lean
- Bullish toward 595 by the near expiry
- Best case
- SPY just below 595 on day 21
- Position after the near expiry
- A long 60-day 585 call if the short leg expires worthless
Commissions, exchange fees, financing and the bid/ask spread are excluded. On a multi-leg position the spread is usually the largest of these. Check the payoff curve for your own strikes — the loss bound is not automatic in a diagonal.
Common questions
What is a "poor man's covered call"?
A diagonal where the long leg is a deep in-the-money, long-dated call standing in for the 100 shares, with a short-dated out-of-the-money call sold against it. It replicates a covered call for far less capital, and adds the risk that the long call decays where shares would not.
Related strategies
- Calendar SpreadNeutral — long volatility of time
- Bull Call SpreadBullish — moderate, defined range
- Covered CallNeutral to mildly bullish — income
- Call CondorNeutral — range-bound
Educational only. This page explains how a structure behaves; it is not a recommendation to trade it. Options and futures carry substantial risk, and short and leveraged positions can lose more than the amount originally invested.