Short Put Calculator

Short Put at a glance

How a short put works

When you sell a put you accept an obligation to buy 100 shares per contract at the strike if the holder exercises. In a margin account your broker does not reserve the full purchase amount. Instead it holds a margin requirement that is a fraction of the strike value and recalculates it every day as the stock moves. That leverage is what defines a naked put: the same capital can support more contracts than a cash secured put, which magnifies both returns and losses.

At expiration the payoff is flat at the full credit for any price at or above the strike. Below the strike the line slopes down one for one, and you lose money once the stock falls under the strike minus the premium. The worst case is the stock going to zero, where the loss equals the strike minus the premium. The risk is large but defined, and it resembles owning the stock from the breakeven price without any of the upside.

Before expiration, the put's time value decays in your favor, and falling implied volatility helps as well. A selloff hurts in two ways at once: the put gains intrinsic value and implied volatility usually jumps, so the mark to market loss can exceed what the stock move alone suggests. Because margin requirements rise as the stock falls, a leveraged naked put can force you to add funds or close positions during a decline. That is the key practical difference from a fully funded put.

Short Put example with real numbers

With the stock at $100, implied volatility at 30%, a 4.1% risk free rate and no dividend, you would sell 1 97.5 put (32 days) at $2.27. That is a net credit of $227. At expiration a maximum profit of $227 and a maximum loss of $9,523, with a breakeven at $95.23. The lognormal chance of profit is 71%.

These are theoretical American option prices from the Bjerksund and Stensland model, not live quotes. Load any ticker in the short put calculator above to run the same math on real market prices.

When to use a short put

• You are neutral to bullish and willing to own the stock at the strike minus the premium.
• Implied volatility is high and you expect it to settle, which makes put premiums attractive to sell.
• You want positive theta exposure and hold margin approval for uncovered options.
• You prefer to use margin efficiently rather than tie up the full strike value in cash.

Max profit, max loss and breakeven

Maximum profit

Premium received times 100 per contract. You keep the full credit if the stock closes at or above the strike at expiration.

Maximum loss

Strike price minus premium received, times 100, if the stock falls to zero. The loss is defined, but with leverage it can be very large relative to the margin you posted.

Breakeven

Strike price minus premium received per share. Below this price at expiration the short put loses money.

Short Put Greeks

• Delta: Delta is positive, so the position gains as the stock rises. An out of the money short put starts with a modest positive delta that grows toward one per share as the stock falls through the strike.
• Gamma: Gamma is negative. As the stock drops your long exposure grows and losses accelerate, with the effect strongest near the strike close to expiration.
• Theta: Theta is positive. Each day without a decline adds to your profit as the put's time value melts.
• Vega: Vega is negative. Rising implied volatility, common in selloffs, raises the put's price and hurts the position.

See the live numbers for your position in the Greeks tab of the calculator, or explore a single option in the options Greeks calculator.

Early exercise and assignment risk

Deep in the money American puts are the options most likely to be exercised early. Once a put is far below the strike it holds little time value, and the holder can exercise to collect the strike in cash and earn interest on it. Higher interest rates make this more common. If you are assigned, you buy 100 shares per contract at the strike, and in a margin account that purchase may create a margin loan. Watch the extrinsic value in the calculator, because assignment risk rises as it approaches zero.

Dividends shift the timing. Put holders gain from the stock's drop on the ex dividend date, so early exercise of in the money puts tends to come right after the ex date rather than before it. After assignment you own the shares outright, with full downside exposure and only the premium you already collected as a cushion. Many traders close or roll an in the money short put before it gets deep enough to attract exercise, and they close before the last session to sidestep pin risk at the strike.

The calculator's Early exercise risk tab flags short legs that are likely to be assigned. For a single option, use the early exercise calculator or read how early exercise and assignment work.

Pros and cons

How to manage a short put

• Size positions by the stock value you would control on assignment, not by the margin requirement.
• Buy a lower strike put to convert into a bull put spread when you want a hard floor on losses.
• Roll down and out for a net credit when the stock tests the strike and you still like the outlook.
• Close early once most of the credit is captured, since the leftover premium pays little for the risk that remains.

Short Put FAQ

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Educational tool, not financial advice. Calculations are theoretical and depend on your inputs; real fills, fees, early assignment and dividends can change results. Options involve risk and are not suitable for every investor.