Calendar Spread Calculator
A long calendar spread sells a near-term option and buys a longer-dated option at the same strike, profiting from faster time decay on the short leg. The cost and the maximum risk are simple arithmetic; the maximum profit is not, because it depends on the surviving long option's value at front-month expiration, which is driven by implied volatility. This calculator returns the figures that are deterministic: the net debit per share, the total cost, the maximum loss, and the value the long option must retain at the near-term expiration to break even.
Calendar spread formula
Net debit per share = long-dated premium - short-dated premium
Total cost = net debit per share * multiplier * number of spreads
Max loss = total cost (long calendar)
Long value needed at front expiry = net debit per share (if short expires worthless)
If the short leg expires worthless at the strike, the long option must be worth at least the net debit per share to recoup the cost. Maximum profit is not a fixed arithmetic value because it depends on implied volatility and the long option's remaining time value.
Using the result
- A long calendar is always a net debit because the longer-dated option costs more at the same strike.
- Maximum loss is capped at the debit paid: a defined-risk position.
- The trade benefits from the short leg decaying faster than the long leg (positive theta).
- It also benefits from rising implied volatility (positive vega) on the long leg.
- Use an option pricing model with a volatility assumption to estimate the upside, which this tool does not assume.
Calendar spread: frequently asked questions
What is a calendar spread?
A calendar spread, also called a time or horizontal spread, sells a near-term option and buys a longer-term option at the same strike and of the same type. It is a net debit position that profits from time decay on the short leg and from a rise in implied volatility, with the underlying ideally near the strike at the near-term expiration.
How do you calculate the net debit of a calendar spread?
The net debit equals the premium paid for the long-dated option minus the premium received for the short-dated option, all per share. Multiply by the contract multiplier to get the dollar cost. Because the longer-dated option always costs more at the same strike, a long calendar is always a net debit.
What is the maximum loss on a calendar spread?
The maximum loss on a long calendar spread is limited to the net debit paid, times the contract multiplier. This worst case occurs if the underlying moves far from the strike, so both options lose most of their value together and the spread collapses toward zero.
Why can't a calendar spread's max profit be a fixed formula?
Maximum profit depends on the price of the still-living long option when the short option expires, which is driven by implied volatility and time remaining. Those are model-dependent, not arithmetic, so a deterministic calculator cannot output a single max-profit number without an option pricing model and a volatility assumption.
What does the breakeven credit needed mean?
It is the residual value the long option must retain at the near-term expiration for the trade to break even, equal to the net debit paid plus what is left of the short option's value. Used as a benchmark: if you expect the long leg to be worth more than the net debit at front-month expiration, the trade has positive expectancy.
Official sources
- U.S. SEC Investor.gov: Options glossary.
- The Options Clearing Corporation (OCC): Standardized options education.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.