A long put calculator shows the profit and loss of a bought put at expiration: the position gains when the stock falls, breaks even at the strike minus the premium paid, and caps its upside because a share price cannot drop below zero. Buy one contract at a $100 strike for $4.00 and you risk $400, break even at $96, and could collect up to $9,600 if the stock collapses to nothing. This page explains the payoff shape, walks through the math with a worked example, and compares the strategy against shorting the stock or buying a debit spread. It is written for education, not financial advice.
What this calculator computes
The long put calculator takes your strike price, the premium you paid per share, the number of contracts, and an assumed price for the underlying at expiration, and it returns the dollar profit or loss, the breakeven, the maximum profit, and the maximum loss. The strategy is a bearish bet: you own the right, not the obligation, to sell 100 shares at the strike. The buyer pays a debit up front and wants the share price to drop.
Long Put Calculator
Calculate the profit and loss of buying a put option at expiration. Enter the underlying price, strike, premium paid, and contracts to see your max profit, max loss, breakeven, Black-Scholes theoretical premium, the full Greeks, probability of profit, and a price-by-price payoff table. Built for US equity options at 100 shares per contract.
Recommended tools and brokers
This calculator models long put profit and loss at expiration using standard US options conventions (100 shares per contract). The Black-Scholes theoretical premium, Greeks, and probabilities are model estimates, not guarantees. It does not model early exercise, commissions, bid-ask slippage, assignment of the short stock, or mid-trade P&L (which differs from expiration P&L because of theta and vega). For education only, not financial advice. Verify quotes and Greeks with your broker before trading.
Three numbers anchor every result. Breakeven sits at the strike minus the premium. Maximum profit equals the strike minus the premium, times 100, since the stock floor is zero. Maximum loss equals the full debit, because the worst case is the option expiring worthless.
The tool assumes standard US equity options: one contract controls 100 shares, and the figures reflect value at expiration rather than mid-trade marks. It suits a trader sizing a bearish position, a hedger pricing downside protection on shares already owned, or a student checking how a defined-risk bet behaves. For deeper input handling you can cross-check the numbers against the call and put calculator, which covers both option types side by side.
How to use the calculator
The math behind a long put
Four formulas drive the result, each scaled by the 100-share multiplier. Breakeven is the strike minus the premium. Maximum profit is (strike minus premium) times 100, reached only if the stock falls to zero. Maximum loss is the premium times 100. Profit at any expiration price equals (the option’s intrinsic value minus the premium) times 100, where intrinsic value is the strike minus the share price, floored at zero.
Here is a concrete case. You buy one contract with a $100 strike for $4.00 per share. The debit is $400. Breakeven lands at $96 (100 minus 4). If the stock drops to $80, the option is worth $20 of intrinsic value, so profit is (20 minus 4) times 100, or $1,600. That is a 400% return on the $400 at risk. If the stock finishes anywhere at or above $100, the contract expires worthless and you lose the whole $400.
| Stock at expiration | Option intrinsic value | Profit / loss per contract |
|---|---|---|
| $120 | $0 | -$400 |
| $100 | $0 | -$400 |
| $96 | $4 | $0 |
| $90 | $10 | +$600 |
| $80 | $20 | +$1,600 |
| $0 | $100 | +$9,600 |
Greeks describe how the price moves before expiration. Delta is negative, near -0.50 at the money, so the option gains as shares fall. Theta is negative: time decay works against the buyer every day. Vega is positive, meaning a jump in implied volatility lifts the contract’s value. Those mid-trade effects do not show in the expiration table, which is why the trade can lose money even on a small down move if volatility drops or time runs out.
Long put vs short stock vs debit spread
A long put is one of three common ways to profit from a falling stock. Shorting the stock has no defined floor on losses and ties up margin. A debit spread, where you buy one contract and sell a lower-strike one, lowers the cost but caps the gain. The right pick depends on conviction and how much you want to spend.
| Position | Cost / capital | Max loss | Max profit |
|---|---|---|---|
| Long put | Premium only | Premium paid | Large, capped at strike value |
| Short 100 shares | Margin + borrow | Unlimited as stock rises | Large, capped at strike value |
| Debit spread | Net debit (lower) | Net debit | Capped at strike width |
When does the simpler, lower-reward choice win? Picture a stock you expect to drift down a few points, not crash. The spread costs less and decays slower, so a modest decline can net more than an outright option that you overpaid for in rich volatility. Buy the standalone contract when you want open-ended downside and can stomach the full premium at risk. For the cash-collateral version of a bullish counterpart, the cash secured put calculator shows how selling premium flips the payoff. You can model multi-leg structures in our options trading calculator before committing capital.
Risk and assignment
As the buyer of a long put, you control exercise; you are not subject to surprise assignment. US equity options are American-style, so you can exercise any time before expiration, though selling to close usually captures more value than exercising early. If you do exercise, you sell 100 shares per contract at the strike. In-the-money contracts are auto-exercised at expiration by the clearinghouse unless you instruct otherwise.
The defined risk is the appeal. A long option can lose 100% of the premium and no more, so your worst case here is the $400 debit. Pin risk matters mainly to option sellers; as a buyer your main enemy is time. Read the OCC disclosure, Characteristics and Risks of Standardized Options, before trading. Every figure on this long put calculator reflects value at expiration; before that date, theta and vega push the mark around. This is education, not financial advice.
FAQ
What is the breakeven on a long put?
The breakeven on a long put is the strike price minus the premium paid. Buy a $100 strike for $4.00 and the stock must close at or below $96 at expiration for the position to turn a profit.
What is the maximum profit on a long put?
Maximum profit equals the strike minus the premium, times 100 shares per contract. It is large but not unlimited, because a stock cannot fall below zero. A $100 strike bought for $4.00 caps out at $9,600 if shares go to zero.
How much can I lose buying a put?
Your maximum loss is the premium you paid, which is 100% of the debit. A $4.00 contract costs $400, and that $400 is the most you can lose no matter how high the stock climbs.
Is a long put better than shorting the stock?
A long put caps your loss at the premium, while a short stock position carries unlimited loss if the price rises. Shorting can be cheaper to hold over time and has no expiration, so neither is universally better; it depends on your timeframe and risk tolerance.
When will the interactive calculator be available?
The interactive long put calculator is coming soon to this page. Until it launches, you can work the formulas above by hand or use the linked sibling tools to model your strike, premium, and expiration price.
