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Calendar Spread Calculator

Model your calendar spread before you place it. Enter your strike, front-month premium received, and back-month premium paid to instantly see net debit, max loss, and a full P&L diagram.

Net Debit Strategy Profits from Time Decay Defined Max Loss Interactive P&L Diagram

Underlying Asset

$
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Strategy Template (optional — pre-fills legs below)

Option Legs

Legs with different expirations are supported (calendar spreads). Implied Vol % is used by the Black-Scholes engine for theoretical pricing.

Getting Started

How to Use This Calculator

Three inputs are all you need. Results update instantly as you type.

1

Enter the strike price

Enter the strike price used for both legs of the spread. A calendar spread uses the same strike for the short and long option — typically near the current stock price to maximize the time value difference.

2

Enter front-month premium

Enter the premium per share received for selling the near-term option. This is the short leg. The faster time decay of the front-month option is the primary profit driver in a calendar spread.

3

Enter back-month premium

Enter the premium per share paid for the longer-dated option. The difference between back-month and front-month premiums equals your net debit — the most you can lose on the position.

4

Review your results

The calculator shows your net debit, max loss, estimated profit zone, and a full P&L diagram illustrating how the position performs at the front-month expiration date.

Strategy Breakdown

Understanding the Calendar Spread

Key numbers every calendar spread trader needs to know before entering the position.

Max Profit
Stock at Strike at Front-Month Expiry
Max profit is achieved when the stock closes right at the strike price at the short option’s expiration. The short option expires worthless and the long back-month option retains maximum time value, widening the spread to its peak value.
Max Loss
Net Debit Paid
Occurs when the stock moves far away from the strike in either direction by expiration, causing both options to lose time value and the spread to collapse toward zero. Your loss is capped at the net debit you paid to enter.
Breakeven
Two Points Flanking the Strike
Calendar spreads have an upper and lower breakeven. The exact prices depend on implied volatility and time remaining in the back-month option at expiration, so they are estimated rather than fixed at entry.

The calendar spread is a time decay strategy that exploits the difference in theta (time decay) between two options at the same strike but different expirations. Near-term options decay faster than longer-dated ones, especially as expiration approaches. By selling the fast-decaying front-month option and owning the slower-decaying back-month option, you benefit when time passes and the stock stays near your chosen strike.

Calendar spreads are ideally entered when implied volatility is low. Low IV means you pay less for the back-month option, reducing your net debit. If IV rises after entry, the back-month option gains more value than the short option loses, giving you an additional tailwind. The trade is sensitive to large moves in either direction, which is why many traders use them during low-volatility, range-bound periods in the market.

After the front-month option expires, you are left holding the back-month option outright. At that point, you can sell another near-term call or put to create a new calendar spread, continuing to collect premium and reduce your cost basis over multiple cycles.

Worked Example

Calendar Spread Example Trade

XYZ is trading at $100. You sell a 30-day $100 call for $2.00 and buy a 60-day $100 call for $4.00.

Position Summary
Stock Price$100.00
Strike Price (Both Legs)$100.00
Front-Month Premium Received (30-day)+$2.00 / share (+$200)
Back-Month Premium Paid (60-day)−$4.00 / share (−$400)
Net Debit−$2.00 / share (−$200)
Max Loss−$200 (net debit, if stock moves far from $100)
Best OutcomeStock at $100 at 30-day expiry (short call expires worthless)
After Front-Month ExpiryStill hold 30-day $100 call — can sell another front-month call
Breakeven RangeApproximately $95 – $105 (depends on IV at expiry)
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FAQ

Calendar Spread — Common Questions

A calendar spread (also called a time spread or horizontal spread) involves selling a near-term option and buying a longer-dated option at the same strike price. Both legs use the same underlying and strike but different expiration dates. The strategy profits from the difference in time decay rates: the short front-month option decays faster than the long back-month option. If the stock stays near the strike at the short option’s expiration, the spread value increases and you profit.
The maximum profit on a calendar spread is achieved when the stock closes right at the strike price at the front-month expiration. At that point, the short option expires worthless and the back-month option retains maximum time value, creating the largest spread between the two legs. The exact dollar amount depends on implied volatility and time remaining in the back-month option at expiration, which is why max profit is estimated rather than fixed. It is typically 50–100% of the net debit paid, and can exceed that in high-volatility environments.
The maximum loss on a calendar spread is the net debit paid to enter the position. This occurs when the stock moves far away from the strike price in either direction, causing both options to lose their time value and the spread to collapse toward zero. Because you are long the back-month option, the spread cannot go below zero, so your loss is strictly capped at what you paid. This makes the calendar spread a defined-risk strategy.
A calendar spread has two breakeven points — one above the strike and one below the strike. Unlike a single-expiration spread, the exact breakeven prices cannot be precisely calculated at entry because they depend on the time value remaining in the back-month option at expiration, which is driven by implied volatility. Higher implied volatility at expiration widens the profitable zone; lower volatility narrows it. As a rough guide, breakeven points are often 3–7% above and below the strike for a 30-day front-month expiration.
A calendar spread uses the same strike price for both the short and long option, differing only in expiration date. A diagonal spread uses different strike prices and different expiration dates. The poor man’s covered call is a well-known example of a diagonal spread, where the long leg is a deep in-the-money LEAPS and the short leg is an out-of-the-money near-term call. Calendar spreads profit most when the stock stays near the shared strike, while diagonal spreads can be structured with a directional bias depending on how the strikes are selected.

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