Buying a single stock option is a contract, not a share, and the math behind whether it made or lost money is surprisingly simple once you separate the price you paid from the price at which the contract finally settled. This stock options calculator estimates your expiration payoff, the net profit after subtracting the premium, the breakeven share price, and your percentage return on the capital you put at risk. It works for both calls and puts, and it scales automatically for the standard contract size of 100 shares.
Pick Call or Put, type in the stock price you expect at expiration, your strike, the premium you paid per share, and how many contracts you bought. Every figure on the result card updates instantly, so you can stress-test a trade at several future share prices before you ever place it.
How to Use
- Choose the Option Type — Call if you expect the underlying stock to rise above the strike, Put if you expect it to fall.
- Enter the Stock Price at Expiry — the share price on the day the option contract expires. This is your price target; the calculator tells you exactly what the contract is worth when the clock runs out.
- Set the Strike Price — the price at which the contract lets you buy (a call) or sell (a put) the underlying shares.
- Type the Premium per Share — the market price you paid for each share the contract covers. This is the most you can lose on a long option.
- Enter the Number of Contracts. One standard US equity contract always covers 100 shares, so two contracts cover 200 shares, three cover 300, and so on.
The result card then shows the payoff per share, the gross payoff on the whole position, the total premium you paid, the net profit, the breakeven price, and your return on investment. If the stock price at expiry is below the call strike (or above the put strike), the option expires worthless and your net loss equals the premium you paid.
The Expiry Payoff Formula
At expiration, an option only has value if it is in the money. The formula taught by the CBOE and used on every broker's payoff diagram is:
- Call payoff per share = max(0, S − K)
- Put payoff per share = max(0, K − S)
Where S is the stock price at expiry and K is the strike price. You then multiply by 100 shares for each contract and subtract the premium you paid:
Net Profit = payoff per share × 100 × contracts − premium per share × 100 × contracts
The breakeven price is the share level where gross payoff exactly equals the premium: K + premium for a call, and K − premium for a put.
Worked example: you pay $5 per share ($500 for one contract) for a call with a $100 strike. If the stock closes at $110 on expiry, the payoff per share is $10, the gross payoff is $1,000, and after the $500 premium your net profit is $500 — a 100% return on the capital you risked. The breakeven price is $105: below that, the trade loses money no matter how small the loss feels.
Calls vs. Puts at a Glance
A call gives you the right to buy shares at the strike. It profits when the stock rises above strike plus premium. Losses are capped at the premium paid; gains are theoretically unlimited. A put gives you the right to sell shares at the strike. It profits when the stock falls below strike minus premium. Losses are again capped at the premium, and gains are largest when the stock collapses toward zero.
The single most common beginner mistake is ignoring the breakeven price. A call that finishes "in the money" at $102 with a $100 strike and a $5 premium still loses money, because the payoff ($200) never covers the $500 premium. Always trade around the breakeven, not around the strike.
Examples
Example 1 — A winning call. You buy one AAPL call with a $100 strike for a $5.00 premium per share. At expiry the stock is $110. Payoff per share is $10, gross payoff is $1,000, premium paid is $500, net profit is $500, breakeven is $105, and ROI is +100%.
Example 2 — A winning put. You buy one put with a $100 strike for a $4.00 premium. The stock drops to $90. Payoff per share is $10, gross is $1,000, premium is $400, net profit is $600, breakeven is $96, and ROI is +150%.
Example 3 — An out-of-the-money call. You keep the same $100 call at a $5 premium, but the stock only reaches $95 at expiry. The payoff is $0, the option expires worthless, and your net profit is −$500 — a −100% loss. The breakeven of $105 was never touched.
Example 4 — Multi-contract sizing. Three puts at a $2 premium per share cover 300 shares. If the stock drops from $75 to $50, the payoff is $25 per share, gross payoff is $7,500, premium is $600, and net profit is $6,900 on a $600 outlay — a 1,150% return.
FAQ
How is an option's profit calculated?
Take the payoff per share at expiration, multiply it by 100 for each contract, and subtract the premium you paid. A call's payoff per share is max(0, stock price at expiry minus strike); a put's is max(0, strike minus stock price at expiry). The result is your net dollar profit or loss on the position.
What is the breakeven price for a call option?
For a long call, breakeven equals the strike price plus the premium per share. If you pay a $5 premium for a $100-strike call, the stock must close above $105 at expiry for the trade to be profitable after fees. Below $105, you lose money even if the option is technically in the money.
What is the breakeven price for a put option?
For a long put, breakeven equals the strike price minus the premium per share. A $100-strike put bought for $4 breaks even at $96: the stock must fall below $96 for the position to net a profit.
What is the most I can lose on a long option?
As the buyer of a call or put, your maximum loss is the premium you paid up front. If the option expires out of the money, it simply vanishes worthless and you lose 100% of that premium. This capped-loss structure is why options are often used for defined-risk strategies.
Why do options cover 100 shares per contract?
Standard US equity options are written on 100 shares of the underlying stock. So a quoted premium of $5.00 per share actually costs $500 per contract ($5 × 100). Multiplying by 100 is the step most new traders forget, which is why the calculator applies it automatically.
Does this calculator account for commissions and fees?
No. It models the pure expiry payoff and net profit after the option premium only. Your broker's per-contract commission, exchange fees, and any slippage on entry or exit will reduce the net figure slightly. Add $0.65 per contract or your broker's schedule to estimate the real number.
When should I use this calculator versus a Black-Scholes model?
Use this expiry-payoff calculator for planning trades, sizing positions, and mapping the profit zone. Use a Black-Scholes calculator when you need the fair market value of an option before expiration, implied volatility, or the Greeks (delta, gamma, theta, vega). This tool assumes you hold the contract all the way to expiry.
Disclaimer
This stock options calculator is provided for informational purposes only and does not constitute investment, financial, tax, or legal advice. Payoff figures are based on the exact inputs you enter and the standard expiry-payoff formula; they do not account for commissions, slippage, assignment risk, early exercise, dividends, or changes in implied volatility before expiration. Options involve substantial risk and are not suitable for every investor. Past or modeled outcomes are not guarantees of future results. Always consult a licensed financial advisor or your broker before trading options with real capital.