How this instrument works
A long call or put option's payoff is not what the contract is intrinsically worth at expiry — it is what is left after subtracting the premium already paid to own it. Intrinsic value is simple: a call is worth the amount the stock finished above the strike, a put is worth the amount it finished below, and zero if the stock lands on the wrong side, because nobody exercises an option for less than doing nothing. The premium then reduces that figure by a fixed amount, since it was paid upfront and cannot be un-paid, no matter what the stock later does.
This is the arithmetic a retail option buyer runs on expiration day, not the calculation a trader runs weeks out while deciding what to pay for a contract. Before expiry, a quoted premium bundles two things — intrinsic value and time value, the latter driven by how much the stock could still move and priced by models such as Black-Scholes. At expiry, time value has fully decayed to zero, so all that remains is the arithmetic this instrument performs: intrinsic value minus what you paid.
The two breakeven lines answer a narrower but more commonly confused question: not when does this option have value, but when does owning it stop being a loss. A call breaks even at strike plus premium because every dollar of intrinsic value between the strike and that point simply repays what was spent; a put breaks even at strike minus premium for the same reason run in reverse. The model assumes a single expiration date, no dividends, no early exercise, and a long position only — a short seller's risk and payoff are the mirror image and are not covered here.
- Enter the Spot price at expiry, $ — the price you expect, or already saw, the underlying trade at when the contract expires.
- Enter the Strike price, $ written on the contract you hold.
- Enter the Option premium paid, $ — the price you paid per share to buy the call or the put.
- Compare Call option net payoff and Put option net payoff side by side to see which position that closing price would have rewarded.
- Check Call breakeven price and Put breakeven price to see the spot price each contract needs to clear before it turns a profit.
Worked example — the $100 strike bought for $3
Say you bought a $100-strike call and, for comparison, a $100-strike put on the same stock, each for a $3 premium, and the stock closed at $105 the day the contracts expired. The call's intrinsic value is max(0, $105 − $100) = $5, worth exercising, but subtracting the $3 paid for it leaves a net payoff of $2.00. The put's intrinsic value is max(0, $100 − $105) = $0, so it expires worthless and the full $3 premium is lost, a net payoff of −$3.00.
The breakeven prices explain why: the call needed the stock above its $103.00 breakeven ($100 strike plus $3 premium) to turn a profit, and $105 clears that bar by $2, exactly the net payoff shown. The put needed the stock below its $97.00 breakeven ($100 strike minus $3 premium), and $105 is nowhere close, which is why it lost the entire premium rather than a partial amount.
Questions
Why does the put lose the whole premium instead of a partial amount?
Because at $105 the put has zero intrinsic value — max(0, $100 − $105) works out to $0, not a negative number — so nothing offsets the $3 already paid. A long option can never lose more than its premium; that floor is what max(0, ·) enforces in the formula, and it is the one asymmetry that separates buying options from buying the stock itself, which can fall without limit.
What is the difference between breakeven and the strike price?
The strike price is where intrinsic value turns positive; breakeven is where the position actually turns a profit after the premium is repaid. A $100-strike call bought for $3 starts paying out the moment the stock passes $100, but every dollar between $100 and $103 just repays the premium — profit only begins past $103, the true breakeven.
Does a negative payoff mean I owe money?
No. A negative payoff on a long call or put means you lose part or all of the premium already paid upfront, not that you owe anything further. The premium becomes a sunk cost the moment you buy the contract; this calculator shows how much of it comes back, never a bill. Selling uncovered options carries open-ended risk, but that is a different position from the long calls and puts modeled here.
Why doesn't this match the price my broker quotes before expiry?
Because this sheet prices the contract only at expiry, using intrinsic value alone. Before expiration, an option also carries time value — priced by models like Black-Scholes from volatility, time remaining, and interest rates — which shrinks toward zero as expiry approaches. A call trading above its intrinsic value today is normal; by the final session that gap closes to what this calculator computes.
Can I use this for options I plan to sell rather than buy?
Not directly. The formulas here assume a long position, meaning you paid the premium to buy the contract, so the sign convention flips for a seller, who collects the premium upfront and owes the intrinsic value at expiry instead. A short call or put's payoff is the mirror image of what is shown here, with materially different, and larger, risk on the losing side.
Does the calculator account for commissions or assignment fees?
No. It works the arithmetic of intrinsic value against the premium paid, exactly as the formula defines it — broker commissions, exercise and assignment fees, and any tax treatment on the gain or loss are excluded and vary by brokerage, so add them separately to see the amount that actually lands in your account.
References
Read this first: This instrument shows arithmetic, not advice. Real offers add fees, taxes and terms that vary by lender and place — verify the figures against your actual paperwork before deciding anything.