🎯 In 30 seconds: A put gives its buyer the right to sell 100 shares at the strike price until expiration. A put buyer profits at expiration if the stock ends below strike minus premium, and can lose at most the premium. Puts can be a bet on a fall or insurance on shares you own. A put seller collects the premium and must buy 100 shares at the strike if assigned, even if the stock has collapsed. That is a large, real risk.
What a put is, in one line
A put option is a contract that gives you the right, but not the obligation, to sell 100 shares of a stock at a fixed price (the strike) until a fixed date (the expiration). You pay a premium for that right.
A put gains value when the stock falls. If you have the right to sell at $48 and the stock is at $40, that right is worth $8 per share, because you could buy at $40 and sell at $48.
New to the vocabulary? Start with What an option is, then Call options. Puts are the mirror image of calls.
Our hypothetical setup for this chapter: Company X trades at $50. A $48 put expiring in about 60 days costs $1.40 per share, or $140 per contract.
Buying a put: the three numbers
| Maximum loss = premium x 100 | $1.40 x 100 = $140 |
| Breakeven = strike - premium | $48 - $1.40 = $46.60 |
| Maximum gain = (strike - premium) x 100 | $46.60 x 100 = $4,660, only if the stock goes to $0 |
The profit or loss at expiration for one long put is:
P/L = (max(strike - stock price, 0) - premium) x 100
Unlike a call, a put's gain has a ceiling, because a stock cannot fall below zero. It is still a large ceiling compared with what you paid.
Worked example: one put at five prices
Hypothetical. You buy one Company X $48 put for $1.40 and hold it to expiration.
| Stock at expiration | Put value per share | Value of 1 contract | Profit or loss | Return on $140 |
|---|---|---|---|---|
| $55 | $0 | $0 | -$140 | -100% |
| $48 | $0 | $0 | -$140 | -100% |
| $47 | $1.00 | $100 | -$40 | -29% |
| $46.60 | $1.40 | $140 | $0 | 0% |
| $42 | $6.00 | $600 | +$460 | +329% |
The stock fell from $50 to $47, a 6% drop, and the put buyer still lost money. A put on a $50 stock with a $48 strike needs the stock to fall more than 6.8% by expiration just to break even. Being right about the direction is not enough. You need the size and the timing too.
Selling the put before expiration
As with calls, most put buyers close the position by selling the put back rather than exercising it.
Hypothetical. Twenty days after you bought, Company X drops to $46. With 40 days left, a pricing model values the $48 put at about $2.89.
| Sold: $2.89 x 100 | $289 |
| Paid: $1.40 x 100 | -$140 |
| Profit before fees | +$149 |
Its value at expiration with the stock still at $46 would be $2.00. The extra $0.89 is time value, which the market pays for the chance the stock falls further before expiration. See What an option is worth.
A put compared with short selling
The other way to bet on a fall is short selling: borrowing shares, selling them and buying them back later. Compare the two for 100 shares of Company X at $50:
| Short 100 shares at $50 | Buy one $48 put at $1.40 | |
|---|---|---|
| Money at risk | no fixed limit, losses grow as the stock rises | $140, fixed |
| Stock rises to $65 | -$1,500 | -$140 |
| Stock ends at $50 | $0, minus borrow fees | -$140 |
| Stock falls to $42 | +$800 | +$460 |
| Time limit | none, but borrow can be recalled | expires in 60 days |
| Account needed | margin account | options approval |
The put limits the loss and caps the cost of being wrong. You pay for that with the premium and the deadline.
Puts as insurance: the protective put
This is the oldest and most practical use of puts. You own 100 shares of Company X, bought at $50. You are worried about a drop over the next two months but do not want to sell. You buy one $48 put for $1.40.
Now, whatever happens, you can sell your shares for $48 until expiration. Your worst case is locked in:
| Stock loss down to the strike: ($50 - $48) x 100 | -$200 |
| Cost of the put | -$140 |
| Worst case, however far the stock falls | -$340 |
| New breakeven: $50 + $1.40 | $51.40 |
Without the put, a fall to $35 would cost $1,500. With it, the loss is $340. If the stock rises to $60 instead, you make $1,000 on the shares minus $140 for the put, so $860. You gave up $140 of upside to buy a floor.
The car insurance comparison fits. The strike works like the deductible: a $48 strike means you absorb the first $2 of the fall yourself. A higher strike gives better protection and costs more. A lower strike is cheaper and protects only against a bigger fall.
Selling (writing) a put
When you sell a put, you collect the premium and accept an obligation: if assigned, you must buy 100 shares at the strike. Your numbers are the put buyer's numbers flipped.
| Maximum gain = premium x 100 | $140 |
| Breakeven = strike - premium | $46.60 |
| Maximum loss = (strike - premium) x 100 | $4,660, if the stock goes to $0 |
Why would anyone take that trade? Some people want to own Company X anyway and would be happy to buy at $48. Selling the put pays them $140 while they wait. If assigned, their effective purchase price is $46.60, lower than the $50 the stock costs today.
The catch is what happens on bad news. Suppose Company X reports a disaster and falls to $30 before expiration. You must still buy 100 shares at $48:
| Pay the strike: 100 x $48 | -$4,800 |
| Shares are now worth 100 x $30 | $3,000 |
| Premium you kept | +$140 |
| Loss | -$1,660 |
A cash-secured put means you keep the full $4,800 in your account so you can always pay for the shares. A naked put means you sell it on margin without the cash set aside. That can force you to sell other holdings, or face a margin call, at the worst moment. Cash-secured puts and the wheel covers the strategy in detail.
Early assignment on puts
Most US stock options are American style, so a put buyer can exercise any business day. A put that is deep in the money, with little time value left, is the kind most likely to be exercised early. If you sold it, you could be handed 100 shares before expiration without warning. See Exercise, assignment and expiration.
Try it
Pick a stock or broad index ETF you might hold for years and add it to your Watchlist. Look up a put about 5% below today's price, expiring in about two months. On paper, compute: the cost per contract, the worst-case loss on 100 shares with the put, the new breakeven, and the yearly cost if you renewed it six times. Then compute what a put seller at that strike would lose if the stock fell 30%. Write both answers in your trading journal.
- You buy one $48 put for $1.40. What are the maximum loss and the breakeven at expiration? Answer: Maximum loss is $140. Breakeven is $46.60 ($48 - $1.40).
- The stock falls from $50 to $47 by expiration. What happens to that $48 put? Answer: It is worth $1.00 ($100), so you lose $40. Being right about direction is not enough: you need the size and the timing too.
- You own 100 shares bought at $50 and buy a $48 put for $1.40. What is your worst case, and your new breakeven? Answer: The worst case is a $340 loss ($200 of stock decline plus the $140 premium), however far the stock falls. The new breakeven is $51.40.
- You sold a $48 put for $1.40 and the stock falls to $30. What is your loss? Answer: $1,660: you pay $4,800 for shares worth $3,000 and keep the $140 premium.