Credit Spread Calculator
Free, no login · By OptionClaws · Updated 2026-09-28
A credit spread sells one option and buys a further out-of-the-money option of the same type and expiration, so you collect a credit with a fixed worst case. Switch between a bull put spread (below the stock, for a neutral-to-bullish view) and a bear call spread (above the stock, neutral-to-bearish), enter the two strikes and premiums, and see the credit, max profit, max loss, breakeven, return on risk, annualized return, and a model-based probability of profit. All the math happens in your browser.
Illustrative inputs; enter your own. Results are calculated in your browser from the numbers you enter.
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How to use the credit spread calculator
- Choose bull put spread or bear call spread.
- Enter the stock price and the implied volatility you want to model.
- Enter the short strike (the option you sell, closer to the stock) and the long strike (the option you buy, further away), with the premium per share for each.
- Enter the days to expiration and the number of spreads.
- Read the credit, max loss, breakeven, and return on risk, and compare the breakeven to the current stock price on the chart.
How it's calculated
At expiration each option is worth its intrinsic value. The short option costs its intrinsic value to close and the long option pays its intrinsic value back, so the loss beyond the short strike grows until it reaches the long strike, then stops. The width between the strikes minus the credit is therefore the most you can lose.
This page uses the same functions the OptionClaws credit spread scanner uses, so a spread entered here gets the same max loss, breakeven, and probability the scanner would give it.
- Net credit: short option premium minus long option premium, times 100.
- Max profit: the net credit times 100, kept if both options expire out of the money.
- Max loss: (strike width minus net credit) times 100.
- Breakeven, bull put spread: short put strike minus the credit.
- Breakeven, bear call spread: short call strike plus the credit.
- Return on risk: max profit divided by max loss. Annualized return: that times 365 over days to expiration, simple scaling.
- Margin required: equal to the max loss for a defined-risk vertical spread.
- Probability of profit: the lognormal-model chance the stock finishes on the profitable side of the breakeven, using your implied volatility and a 4.5% risk-free rate.
Assumptions and limitations
- Payoff is at expiration only; the chart does not show value before expiration.
- Probability of profit is model-based and uses one implied volatility for both strikes.
- Early assignment of the short leg, dividends, fees, and commissions are not included. A short call can be assigned early ahead of an ex-dividend date.
- Both legs share one expiration.
- Premiums are taken as entered. The starting values are illustrative estimates, not quotes.
Frequently asked questions
- How do you calculate max loss on a credit spread?
- The distance between the strikes minus the credit, times 100. A $5-wide bull put spread collected for $0.90 can lose at most $4.10 times 100, or $410 per spread.
- What is the breakeven on a bull put spread?
- The short put strike minus the credit. A $95/$90 bull put spread for $0.90 breaks even at $94.10 at expiration.
- What is the breakeven on a bear call spread?
- The short call strike plus the credit. A $105/$110 bear call spread for $1.00 breaks even at $106 at expiration.
- Why does a higher probability of profit come with a lower return on risk?
- Moving the short strike further from the stock makes it more likely to expire worthless but lowers the premium, so the credit shrinks while the width, and the max loss, stay about the same.
- How much margin does a credit spread need?
- For a standard vertical credit spread in a margin account, the requirement is the max loss: strike width minus credit, times 100. The options margin calculator covers uncovered positions, where the rules differ.
Related
For education only, not investment advice. Results are model-based estimates from the inputs you enter and exclude fees, early assignment, and dividends. Options involve substantial risk and are not suitable for every investor. See our Terms of Service.