Bull Call Spread Calculator

A bull call spread (also called a call debit spread) is a bullish vertical spread where you buy a call at a lower strike and sell a call at a higher strike, both with the same expiration. You pay a net debit to enter, which is also your maximum loss. In exchange for capping your upside, you reduce your cost compared to buying a call outright.

Key Characteristics

• Maximum Loss: Net debit × 100 × number of contracts. Occurs when the stock closes at or below the long strike at expiration.
• Maximum Profit: (Spread width - net debit) × 100 × number of contracts. Achieved when the stock closes at or above the short strike at expiration.
• Breakeven: Long strike + net debit.
• Best Used When: Moderately bullish with a price target, or when you want better risk/reward than a long call for a specific price target.

How to Read the P/L Chart

The white line (exp) shows your profit/loss at expiration. Below the long strike, you lose the full net debit. Between the strikes, profit increases as the stock rises. Above the short strike, profit is capped—the short call fully offsets the long call beyond this point. The spread's maximum value equals the spread width because you can exercise to buy shares at the long strike and have them called away at the short strike.

The cyan line (T+0) shows your theoretical P/L today. Before expiration, the curve is smoother because both options retain time value. Notice the P/L is more muted compared to expiration—if the stock falls to your long strike or rises to your short strike before expiration, you won't see the full max loss or max profit yet.

As expiration approaches, the cyan line converges toward the white line. Where the T+0 line sits relative to expiration tells you about theta: if T+0 is above expiration, you have negative theta (time decay hurts). If T+0 is below expiration, you have positive theta (time decay helps).

How to Use This Calculator

Enter various spread details into the inputs:

1. Stock Price: Current price of the underlying stock
2. Long Strike: The lower strike where you buy the call
3. Short Strike: The higher strike where you sell the call
4. Days to Expiration: Time remaining until both options expire
5. IV or Prices: Enter implied volatility to calculate theoretical prices, or toggle to enter actual option prices

Then change the inputs to see how the spread metrics change (shift strikes further ITM or OTM, change IV, etc.). You can learn a lot about the strategy by experimenting with the inputs.

When to Use a Bull Call Spread

Bull call spreads work well when you're bullish but have a specific price target. If you think a $100 stock will hit $110 but probably not $120, a bull call spread lets you profit from that move at a lower cost than buying a call outright. The tradeoff: if the stock rockets past your short strike, you don't participate in those gains.

Because spreads cost less than outright calls, your breakeven is lower. This gives you a higher probability of profit and the potential for larger percentage returns—though your dollar profit is capped.

Bull Call Spread vs Long Call

A long call has unlimited upside but costs more than a spread using the same long strike. A bull call spread costs less, has a lower breakeven, and offers a higher probability of profit—but caps your gains. Choose based on conviction: if you expect a huge move, buy the call. If you expect a moderate move, the spread offers better risk/reward.

A Note on Early Assignment

While rare, the short call in your spread can be assigned early—typically when it's deep in-the-money near expiration or just before an ex-dividend date. If assigned, you'll be short 100 shares, but your long call protects you. You can exercise your long call to cover the position, or sell the long call (to close) while buying back the short shares (to close), effectively closing the spread at max profit less any additional fees.