Diagonal Spread
A diagonal spread is an options strategy constructed by simultaneously buying and selling options of the same type (both calls or both puts) on the same underlying asset but with different strike prices and different expiration dates, combining features of both a calendar spread (different expiries) and a vertical spread (different strikes). The resulting position profits from time decay differentials, volatility differences across the term structure, and directional movements within a defined range.
Key takeaways
- Diagonal spreads are formed by combining a long option in a further-dated expiration with a short option in a nearer-dated expiration at a different strike—typically selling a near-term option to partially finance the longer-dated position.
- The term 'diagonal' refers to the visual appearance when options positions are mapped on a grid with strike prices on one axis and expiration dates on the other—the positions form a diagonal line.
- A common implementation is the 'poor man's covered call'—buying a deep in-the-money LEAP call and selling near-term calls against it, mimicking a covered call strategy with less capital commitment.
- Profitability depends on the rate of time decay in the sold near-term option relative to the purchased longer-dated option, the movement of the underlying relative to the short strike, and changes in the volatility term structure.
- Maximum profit typically occurs at expiration of the near-term option when the underlying closes at or near the short option's strike price, and the position retains significant value from the long option.
Explanation
The diagonal spread occupies a conceptual middle ground between the temporal focus of calendar spreads and the directional focus of vertical spreads, combining both elements to create a multidimensional profit potential that is more complex to analyze but potentially more flexible than either strategy alone. The name derives from the grid representation of options: if strikes are plotted on the horizontal axis and expirations on the vertical axis, a diagonal spread's two legs occupy positions on a diagonal line through this grid.
The classic diagonal call spread involves buying a call with a lower strike price and a later expiration while selling a call with a higher strike and an earlier expiration. The initial debit paid for the spread is less than the cost of the long call alone (partially offset by the short call premium), providing a cost-reduction mechanism. The position benefits from three sources: (1) superior time decay on the short near-term option vs. the long far-dated option (theta is higher for near-term options as a percentage of premium); (2) if the underlying rises toward the short strike before near-term expiration, the short call decays maximally; and (3) if implied volatility increases, the longer-dated long option benefits more in absolute premium terms than the short-dated option.
The 'poor man's covered call' (PMCC) variation is particularly popular among institutional investors seeking to replicate covered call strategies with less capital. Instead of buying 100 shares and selling a 1-month call against the position (requiring substantial equity capital), the investor buys a 1-2 year deep in-the-money call (delta ~0.80, acting as a stock surrogate) and sells a near-term call against it. The LEAP call captures most of the stock upside while costing far less than the shares themselves—the difference representing the cost of leverage inherent in the long call. Rolling the near-term short call month by month generates ongoing premium income that progressively reduces the cost basis of the LEAP.
Risk management for diagonal spreads requires attention to several scenarios. If the underlying moves sharply above the short strike before expiration, the short call may need to be bought back at a loss (potentially exceeding the premium received), though this loss is partially offset by the increased value of the long option. If the underlying collapses, both the long and short options lose value, with the spread's maximum loss equal to the initial debit paid. Changes in the volatility term structure—specifically if long-dated implied volatility falls relative to short-dated implied volatility—can erode the value of the spread even without underlying movement.
Formula
Diagonal Spread P&L = (Long Call Value at T₁ - Long Call Purchase Price) - (Short Call Sale Price - Short Call Value at T₁); Maximum Loss = Net Debit Paid
Example
An investor believes a technology stock currently trading at $200 will trend higher over the next six months but expects only modest near-term movement. The investor constructs a diagonal call spread: buys 10 contracts of a 6-month call with a $195 strike (delta 0.55, premium $15.00) and simultaneously sells 10 contracts of a 1-month call with a $210 strike (premium $3.50). Net debit: $15.00 - $3.50 = $11.50 per share, or $11,500 total for 10 contracts. If the stock expires between $200 and $210 at the 1-month expiration, the short $210 call expires worthless (full $3,500 premium retained), and the long 6-month call retains significant time value—perhaps now worth $13.00, for a total spread value of $13.00. After rolling the short call to the next month (selling another near-term call for $3.50), the net cost basis of the long call has fallen from $15.00 to $11.50. Repeating this cycle over six months can dramatically reduce the effective cost of the long-dated option.
Related terms
Back Months Basis Calendar Spread Contract Month Covered Call Deferred Futures Delta Equity Implied Volatility In The Money Leverage Option